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  • Other Sources  (191)
  • METALLIC MATERIALS  (191)
  • 2005-2009
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  • 1984  (191)
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  • 1
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    Fatigue induced cracking in aluminum LN-2 shroud of 39 foot vacuum chamber (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Fourteen years after completion of Ford's 39-foot space simulation chamber, leaks began to appear in its LN2 shroud. Although the shroud had been tight since its acceptance, cracks appeared in 1983 in some of the field welds of the one inch tubes which interconnect the LN2 panels. The resulting leaks were large enough to prevent pump down to high vacuum and could be heard easily when the chamber was at ambient conditions. New cracks appeared during each thermal cycle making it impossible to utilize the chamber for thermal vacuum testing. The analysis presented here implies that many, if not all, of the aluminum LN2 shrouds now in use may be in various stages of fatigue failure. The probability is high that fatigue cracks are working through the aluminum tubing in heat-affected zones of some field welds. The cracks may not be apparent yet, but after the shroud has experienced a certain number of thermal cycles these cracks will work through the material and become serious leaks. Fortunately, appropriate planning, analysis, and checking can, with a relatively small expenditure of money, help to avoid large and unexpected shroud failures and keep the chamber operational as long as it is needed.
    Keywords: METALLIC MATERIALS
    Type: NASA. Goddard Space Flight Center 13th Space Simulation Conf.; p 77-100
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  • 2
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    Thin metal film and multilayers experiment (A0138-3) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The sources of degradation of in state of the art and newly developed components and testing the usefulness of the concept of storing experiment samples in dry nitrogen under launch and space vacuum conditions during reentry mission phase were investigated. Ultraviolet (UV) and extreme ultraviolet (EUV) experiments suffer degradations during space missions of even 1 month duration. It is suggested that the degradation is due to condensation of outgassing products, followed by solar induced polymerization, however, penetrating charged particles are also known to produce volume effects. Degradation may also start immediately after manufacturing of the component due to oxidation, moisture, or chemical corrosion by atmospheric constituents such as CO2 and SO2. When the filters are used as windows for gas absorption cells or gas filters, or when they define the instrumental bandwidth by themselves. The effects of mechanical degradation by thermal cycling and/or dust may cause a dramatic impact.
    Keywords: METALLIC MATERIALS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 159-160
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  • 3
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    A review of our present understanding of macrosegregation in ingots (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: The present understanding of the mechanisms responsible for macrosegregation occurring in ingots produced by electroslag remelting (ESR), vacuum arc remelting (VAR), direct chill (DC), and continuous casting is reviewed. A detailed description is given of laboratory experiments on model Sn-Pb and Al-Cu alloys. The experimental findings are compared with theoretical predictions. Data are also presented on a high-temperature Ni-27 wt % Mo alloy ESR ingot and 2000 series aluminum alloy DC ingots. Comparison is made to theoretical predictions where appropriate.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 169-186
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  • 4
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    Macrosegregation in aluminum alloy ingot cast by the semicontinuous direct chill method (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: A theoretical model of the semicontinuous DC casting method is developed to predict the positive segregation observed at the subsurface and the negative segregation commonly found at the center of large commercial-size aluminum alloy ingot. Qualitative analysis of commercial-size aluminum alloy semicontinuous cast direct chill (DC) ingot is carried out. In the analysis, both positive segregation in the ingot subsurface and negative segregation at the center of the ingot are examined. Ingot subsurface macrosegregation is investigated by considering steady state casting of a circular cross-section binary alloy ingot. Nonequilibrium solidification is assumed with no solid diffusion, constant equilibrium partition ratio, and constant solid density.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 157-168
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  • 5
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    Solidification structures grown under induced flow and continuous casting of steel (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: The use of induced flow as a means to control solidification structures in strand cast steel is investigated. The quality problems in strand cast steel stemming from columnar growth can be partially controlled, by Electro Magnetic Stirring (EMS). Induced flow changes the normal morphology of dendrites. Solids grown under intense stirring conditions show both negative and positive segregation which is considered unacceptable by some steel producers. The inclusion size and population is strongly affected by induced flow (EMS). Laboratory and industrial data show substantial reduction in inclusion size and content, but the overall effect of flow on inclusions is affected by the particular type of flow patterns utilized in each case. Productivity and quality are raised substantially in steel strand casting by utilizing EMS.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 151-156
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  • 6
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    Microsegregation during directional solidification (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: During the directional solidification of alloys, solute inhomogeneities transverse to the growth direction arise due to morphological instabilities (leading to cellular or dendritic growth) and/or due to convection in the melt. In the absence of convection, the conditions for the onset of morphological instability are given by the linear stability analysis of Mullins and Sekerka. For ordinary solidification rates, the predictions of linear stability analysis are similar to the constitutional supercooling criterion. However, at very rapid solidification rates, linear stability analysis predicts a vast increase in stabilization in comparison to constitutional supercooling.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 117-138
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  • 7
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    Characterization of macrosegregation in ESR IN-718 (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: Aspects of macrosegregation theory, such as dendrite arm spacing, pool profile and mushy zone depth are beneficial to developing consumable melting process for Ion Nickel IN-718, Electro-Slag Refining, especially ESR. Aspects of microsegregation theory, such as correlation of dendrite arm spacing with heat transfer mechanisms and local solidification time, are used to minimize remnant dendritism in both ESR and Vacuum Arc Remelting VAR IN-718. Specifically, ESR IN-718 must be optimized by developing practices which maximize ingot cooling rate and minimize the steepness of the solidus and liquidus isotherms. The knowledge concerning macrosegregation in consumable melted IN-718 is in the form of correlations. Since the isotherm steepness is undoubtedly involved, investigations which include a microgravity environment might separate microsegregation effects from macrosegregation effects. Accounting for the effects of gravity and density differences between the metal pool and the interdendritic fluid, in combination with the pool and mushy zone profiles, can lead to improved melting solidification practices for IN-718, and allow prediction of macrosegregation tendency to be incorporated into high temperature alloy design.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 139-150
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  • 8
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    Changes in solidified microstructures (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: The properties and casting behavior of metals are significantly affected by their cast structure. This structure is optimized by producing columnar versus equiaxed grains and coarse versus fine grains by controlling solidification conditions. The transition from columnar to equiaxed grains is favored by: constitutional supercooling with effective nucleation of free dendrites; melting off and transport of dendrite tips and arms; mechanical vibration; falling down of free dendrites from a chilled top surface; and induced flow in the solidifying structure by oscillation of rotation.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 91-104
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  • 9
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    Porosity and environment (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: Significant progress was achieved when it was realized that porosity could be analyzed successfully by considering not only heat flow, but also fluid flow within the solidifying casting. Sound castings may be produced by lowering pressure during melting (to allow dissolved gas to escape the melt) and increasing pressure during solidification (to force liquid metal into the mushy zone to feed shrinkage). Such techniques are especially effective if they are combined with chilling of parts of the casting to produce progressive solidification, which shortens the mushy zone and, hence, the distance that metal must travel to feed porosity.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 71-78
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  • 10
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    The movement of particles in liquid metals under gravity forces and the interaction of particles with advancing solid-liquid interface (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: The problems of shrinkage and gas porosity are discussed. Gravity forces enhance the removal of gas bubbles from a metal melt and contribute to the feeding of shrinkage porosity in castings. Experiments are reviewed which determine how large a density difference is required for metal particles to float or sink in a metal melt and to what extent do factors not considered in Stokes Law influence particle movement in a real system. As to the interaction of particles with an advancing solid-liquid interface, the results indicate that the metal particles are not rejected in a metal melt, and that concentrations of particles in a metal following solidification are due to other factors.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 79-90
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  • 11
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    The potential for bulk undercooling as an industrial process (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: The main focus is on solidification occurring in highly supercooled melts. Solidification rates in such melts are extremely high, an attractive feature from a commercial standpoint. Thus, the reported growth velocities for pure Ni and Co dendrites at a supercooling of 175 K are in excess of 180 km/hr. Rapidly quenched crystalline alloys produced by various atomization processes (e.g., centrifugal atomization or inert gas atomization) or melt spinning are examples of solidification processes, currently being intensively explored commercially, wherein extremely high solidification rates are achieved. Estimated dendrite tip growth rates are about 2 km/hr in a binary Al-4.5 wt % alloy, with a heat transfer coefficient of 6.4x10 sub 5 w/sq cm K or 15 cal/cu cm sK. In the limit, when the solidification rate exceeds a critical value, a glassy microstructure is obtained even in highly alloyed melts, which under normal conditions would solidity to form one or more crystalline phases. Glassy metals, also called metallic glasses, are candidate materials for distribution transformers because of their very low energy losses and are also being used in brazing and soldering applications.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 33-70
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  • 12
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    Bulk undercooling (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: Bulk undercooling methods and procedures will first be reviewed. Measurement of various parameters which are necessary to understand the solidification mechanism during and after recalescence will be discussed. During recalescence of levitated, glass-encased large droplets (5 to 8 mm diam) high speed temperature sensing devices coupled with a rapid response oscilloscope are now being used at MIT to measure local thermal behavior in hypoeutectic and eutectic binary Ni-Sn alloys. Dendrite tip velocities were measured by various investigators using thermal sensors or high speed cinematography. The confirmation of the validity of solidification models of bulk-undercooled melts is made difficult by the fineness of the final microstructure, the ultra-rapid evolution of the solidifying system which makes measurements very awkward, and the continuous modification of the microstructure which formed during recalescence because of precipitation, remelting and rapid coarsening.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 15-32
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  • 13
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    The undercooling of liquids (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: The formation by melt quenching of such metastable structures as glassy or microcrystalline solids and highly supersaturated solutions is made possible by the extreme resistance of most melts to homophase crystal nucleation at deep undercooling. This nucleation resistance contrasts sharply with the very low kinetic resistance to the movement of crystal-melt interfaces, once formed, in metals and other fluid systems at even minute undercooling. The methods of nucleation study which have proven especially effective in bypassing nucleation by heterophase impurities thereby exposing the high resistance of melts to homophase nucleation may be summarized as follows: observation of the crystallization behavior of dispersed small droplets; drop tube experiments in which liquid drops solidify, under containerless conditions, during their fall in the tube; and observation of the crystallization of bulk specimens immersed in fluxes chosen to dissolve or otherwise deactivate (e.g., by wetting) heterophase nucleants. This method has proven to be remarkably effective in deactivating such nucleants in certain pure metals.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 11-14
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  • 14
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    Solidification study of some Ni- and Co-base alloys (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: An ongoing research program aims to characterize the solidification of several Ni- and Co-based commercial wrought type alloys. The techniques used and the data items sought are: (1) thermal analysis, liquidus, nonequilibrium solidus as a function of cooling rate, secondary reactions temperatures, incipient melting, progress of solidification as a function of temperature; (2) optical metallography, characteristic structures and secondary dendrite arm spacing as a function of cooling rate; (3) X-ray diffraction, identification of precipitates; and (4) SEM/EDAX, measure of microsegregation.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 105-116
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  • 15
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    Microwelding of various metallic materials under ultravacuum (A0138-10) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: In the space vacuum environment, the spacecraft mechanisms are liable to sustain damaging effects from microwelds due to molecular diffusion of the spacecraft constituent metals. Such microwelds result in a continuing increase in the friction factors and are even liable to jam the mechanisms altogether. The object of this experiment is to check the metal surfaces representative of the mechanism constituent metals (treated or untreated, lubricated or unlubricated) for microwelds afater an extended stay in the space environment. The experimental approach is to passively expose inert metal specimens to the space vacuum and to conduct end-of-mission verification of the significance of microwelds between various pairs of metal washers. The experiment will be located in one of the FRECOPA boxes in a 12-in. -deep peripheral tray that contains nine other experiments from France.
    Keywords: METALLIC MATERIALS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 35-37
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  • 16
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    Nature of gamma-prime precipitates in rheocast IN-100 alloy (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The microstructures of commercial VIM-cast and rheocast (Apelian and Cheng, 1983) IN-100 superalloy are investigated optically and by two-stage replica TEM, with an emphasis on the nature of the gamma-prime (GP) precipitates. Photomicrographs at magnifications of 39, 390, 2145, and 6630 are presented and discussed. VIM-cast IN-100 has dendritic structure, 10-20-micron primary GP particles, and uniformly distributed cuboid GP precipitates of a uniform size (about 0.5 micron). Rheocast IN-100 (stirred 20 min at 350 rpm, 1291 C, and 0.0006 torr) has a nondendritic structure, 20-100-micron primary GP particles, and a smaller volume fraction of cuboid GP precipitates with a bimodal (either 1-1.5 microns or less than 0.5 micron) size distribution. Such distribution should increase fatigue-crack-nucleation resistance.
    Keywords: METALLIC MATERIALS
    Type: Journal of Materials Science Letters (ISSN 0261-8028); 3; 71-73
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  • 17
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    Friction and wear of some ferrous-base metallic glasses (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Sliding friction experiments, X-ray photoelectron spectroscopy (XPS) analysis, and electron microscopy and diffraction studies were conducted with ferrous base metallic glasses (amorphous alloys) in contact with aluminium oxide at temperatures to 750 C in a vacuum. Sliding friction experiments were also conducted in argon and air atmospheres. The results of the investigation indicate that the coefficient of friction increases with increasing temperature to 350 C in vacuum. The increase in friction is due to an increase in adhesion resulting from surface segregation of boric oxide and/or silicon oxide to the surface of the foil. Above 500 C the coefficient of friction decreased rapidly. The decrease correlates with the segregation of boron nitride to the surface. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and/or silicon oxide at 350 C and boron nitride above 500 C. The segregation of contaminants is responsible for the friction behavior. The amorphous alloys have superior wear resistance to crystalline 304 stainless steel. The relative concentrations of the various constituents at the surfaces of the amorphous alloys are very different from the nominal bulk compositions.
    Keywords: METALLIC MATERIALS
    Type: ASLE Transactions; 27; 295-303;
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  • 18
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    Fracture mechanics and surface chemistry investigations of environment-assisted crack growth (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is pointed out that environment-assisted subcritical crack growth in high-strength steels and other high-strength alloys (particularly in hydrogen and in hydrogenous environments) is an important technological problem of long standing. This problem is directly related to issues of structural integrity, durability, and reliability. The terms 'hydrogen embrittlement' and 'stress corrosion cracking' have been employed to describe the considered phenomenon. This paper provides a summary of contributions made during the past ten years toward the understanding of environmentally assisted crack growth. The processes involved in crack growth are examined, and details regarding crack growth and chemical reactions are discussed, taking into account crack growth in steels exposed to water/water vapor, the effect of hydrogen, reactions involving hydrogen sulfide, and aspects of fracture surface morphology and composition. Attention is also given to the modeling of crack growth response, crack growth in gas mixtures, and the interaction of solute atoms with the crack-tip stress field.
    Keywords: METALLIC MATERIALS
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  • 19
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    Effect of water vapor on fatigue crack growth in 7475-T651 aluminum alloy plate (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The effects of water vapor on fatigue crack growth in 7475-T651 aluminum alloy plate at frequencies of 1 Hz and 10 Hz were investigated. Twenty-five mm thick compact specimens were subjected to constant amplitude fatigue testing at a load ratio of 0.2. Fatigue crack growth rates were calculated from effective crack lengths determined using a compliance method. Tests were conducted in hard vacuum and at water vapor partial pressures ranging from 94 Pa to 3.8 kPa. Fatigue crack growth rates were frequency insensitive under all environment conditions tested. For constant stress intensity factor ranges crack growth rate transitions occurred at low and high water vapor pressures. Crack growth rates at intermediate pressures were relatively constant and showed reasonable agreement with published data for two Al-Cu-Mg alloys. The existence of two crack growth rate transitions suggests either a change in rate controlling kinetics or a change in corrosion fatigue mechanism as a function of water vapor pressure. Reduced residual deformation and transverse cracking specimens tested in water vapor versus vacuum may be evidence of embrittlement within the plastic zone due to environmental interaction.
    Keywords: METALLIC MATERIALS
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  • 20
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    Influence of precracked specimen configuration and starting stress intensity on the stress corrosion cracking of 4340 steel (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Since the pioneer work of Brown (1966), precracked specimens and related fracture mechanics analyses have been extensively used to study stress corrosion cracking. Certain questions arose in connection with initial attempts to prepare standardized recommended practices by ASTM Committee G-1 on Corrosion of Metals. These questions were related to adequacy of test control as it pertains to acceptable limits of variability, and to validity of expressions for stress intensity and crack-surface displacements for both specimen configurations. An interlaboratory test program, was, therefore, planned with the objective to examine the validity of KIscc testing for selected specimen configurations, materials,and environmental systems. The results reported in the present paper include details of a single laboratory test program. The program was conducted to determine if the threshold value of stress intensity for onset and arrest of stress corrosion cracking was independent for the two specimen configurations examined.
    Keywords: METALLIC MATERIALS
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  • 21
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    Chemical reactions involved in the initiation of hot corrosion of IN-738 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Sodium-sulfate-induced hot corrosion of preoxidized IN-738 was studied at 975 C with special emphasis placed on the processes occurring during the long induction period. Thermogravimetric tests were run for predetermined periods of time, and then one set of specimens was washed with water. Chemical analysis of the wash solutions yielded information about water soluble metal salts and residual sulfate. A second set of samples was cross sectioned dry and polished in a nonaqueous medium. Element distributions within the oxide scale were obtained from electron microprobe X-ray micrographs. Evolution of SO was monitored throughout the thermogravimetric tests. Kinetic rate studies were performed for several pertinent processes; appropriate rate constants were obtained from the following chemical reactions; Cr203 + 2 Na2S04(1) + 3/2 02 yields 2 Na2Cr04(1) + 2 S03(g)n TiO2 + Na2S04(1) yields Na20(T102)n + 503(g)n T102 + Na2Cro4(1) yields Na2(T102)n + Cr03(g).
    Keywords: METALLIC MATERIALS
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 131; 2985-299
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  • 22
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    Influence of precracked specimen configuration and starting stress intensity on the stress corrosion cracking of 4340 steel (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Experimental results are presented from a study of the effects of precracked specimen configuration and initial starting stress intensity on crack growth rate and threshold stress intensity, for both onset of cracking and crack arrest. Attention is given to AISI 4340 steel in a 3.5-percent NaCl solution, for configurations of a single edge-cracked specimen tested in cantilever bending under constant load, and a modified compact specimen bolt loaded to a constant deflection. The threshold stress intensity value determined was independent of specimen configuration, if the stress intensity value associated with the compact specimen is taken where the discontinuous break occurs in the velocity-stress intensity curve.
    Keywords: METALLIC MATERIALS
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  • 23
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    Mechanical-contact-induced transformation from the amorphous to the partially crystalline state in metallic glass (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Friction and wear tests were conducted with 3.2- and 6.4-millimeter-diameter aluminum oxide spheres sliding, in reciprocating motion, on a Fe67Co18B14Si1 metallic foil. Crystallites with a size range of 10 to 150 nanometers were produced on the wear surface of the amorphous alloy. A strong interaction between transition metals and metalloids such as silicon and boron results in strong segregation during repeated sliding, provides preferential transition metal-metalloid clustering in the amorphous alloy, and subsequently produces the diffused honeycomb structure formed by dark grey bands and primary crystals, that is, alpha-Fe in the matrix. Large plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminum oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris, and/or powdery-whiskery oxide debris.
    Keywords: METALLIC MATERIALS
    Type: Thin Solid Films (ISSN 0040-6090); 118; 363-373
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  • 24
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    Deformation and fracture behavior of Ni-Mo-Al(gamma/gamma prime-alpha) in situ composite (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Tensile properties of a directionally solidified (DS) eutectic alloy of the nominal composition Ni-33 Mo-5.7 Al (weight percent) have been investigated both at room temperature and elevated temperatures. The microstructure-mechanical property relationship has been studied for the alloy both in the as-DS and heat-treated conditions. Changes in the yield strength, the work hardening behavior, and the fracture morphology have been explained in terms of the microstructural changes due to the heat treatment. The yield drops observed have been attributed to the microdebonding due to the possible segregation of impurities at the fiber-matrix interface, and partly to the strain aging. The deformation mechanism has been identified to be the cutting of gamma prime particles.
    Keywords: METALLIC MATERIALS
    Type: Metallurgical Transactions A - Physical Metallurgy and Materials Science (ISSN 0360-2133); 15A; 1905-191
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  • 25
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    Deformation and erosion of f.c.c. metals and alloys under cavitation attack (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Experimental investigations have been conducted to determine the early stages of cavitation attack on 6061-T6 aluminum alloy, electrolytic tough pitch copper, brass, and bronze, all having polycrystalline fcc matrices. The surface profiles and scanning electron micrographs show that the pits are initially formed at the grain boundaries, while the grain surfaces are progressively roughened by multiple slip and twinning. The initial erosion is noted to have occurred from the material in the grain boundaries, as well as by fragmentation of part of the grains. Further erosion occurred by shearing and necking of the surface undulations caused by plastic deformation. The mean penetration depth, computed on the basis of mass loss, was lowest on the bronze and greatest on the copper. Attention is given to the relation of cavitation attack to grain size, glide stress and stacking fault energy.
    Keywords: METALLIC MATERIALS
    Type: Materials Science and Engineering (ISSN 0025-5416); 67; 55-67
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  • 26
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    Elevated temperature compressive steady state deformation and failure in the oxide dispersion strengthened alloy MA 6000E (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The compressive flow strength-strain rate behavior of the oxide-dispersion-strengthened alloy MA 6000E has been studied in the temperature range 1144-1366 K, with strain rates ranging from 2.1 x 10 to the -5th to 2.1 x 10 to the -7th per s. It is found that the inherent strength of the alloy is essentially the same in all test directions and that the low strength observed in tensile tests results from the inability of grain boundaries to support high tensile stresses. The failure of MA 6000E under high-temperature, slow plastic flow conditions is shown to be the result of concentrated slip. Slow plastic deformation in MA 6000E can be described by a threshold stress model of creep where threshold stresses are calculated from relatively fast testing procedures and the effective stress exponent for creep is assumed to be 3.5.
    Keywords: METALLIC MATERIALS
    Type: Metallurgical Transactions A - Physical Metallurgy and Materials Science (ISSN 0360-2133); 15A; 1753-176
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  • 27
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    Oxidation behavior of a thermal barrier coating (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Thermal barrier coatings, consisting of a plasma sprayed calcium silicate ceramic layer and a CoCrAlY or NiCrAlY bond coat, were applied on B-1900 coupons and cycled hourly in air in a rapid-response furnace to maximum temperatures of 1030, 1100, or 1160 C. Eight specimens were tested for each of the six conditions of bond-coat composition and temperature. Specimens were removed from test at the onset of failure, which was taken to be the formation of a fine surface crack visible at 10X magnification. Specimens were weighed periodically, and plots of weight gain vs time indicate that weight is gained at a parabolic rate after an initial period where weight was gained at a much greater rate. The high initial oxidation rate is thought to arise from the initially high surface area in the porous bond coat. Specimen life (time to first crack) was found to be a strong function of temperature. However, while test lives varied greatly with time, the weight gain at the time of specimen failure was quite insensitive to temperature. This indicates that there is a critical weight gain at which the coating fails when subjected to this test.
    Keywords: METALLIC MATERIALS
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  • 28
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    A study of the effect of solid particle impact and particle shape on the erosion morphology of ductile metals (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Impulsive versus steady jet impingement of spherical glass bead particles on metal surfaces was studied using a gas gun facility and a commercial sand blasting apparatus. Crushed glass particles were also used in the sand blasting apparatus as well as glass beads. Comparisons of the different types of erosion patterns were made. Scanning electron microscopy, surface profilometry and energy dispersive X-ray spectroscopy analysis were used to characterize erosion patterns. The nature of the wear can be divided into cutting and deformation, each with its own characteristic features. Surface chemistry analysis indicates the possiblity of complex chemical and/or mechanical interactions between erodants and target materials.
    Keywords: METALLIC MATERIALS
    Type: Journal of Microscopy (ISSN 0022-2720); 135; 49-59
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  • 29
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    Containerless drop tube solidification and grain refinement of NiAl3 (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The possibility of undercooling Ni-Al alloys below the liquidus in order to produce a single phase peritectic structure by containerless drop tube solidification was studied. Containerless process is a technique for both high purity contamination free studies as well as for investigating the undercooling and rapid solidification of alloys by suppression of heterogeneous nucleation on container walls. In order to achieve large undercoolings one must avoid heterogeneous nucleation of crystallization. It was shown that the Marshall Space Flight Center drop tubes ae unique facilities for containerless solidification experiments and large undercoolings are possible with some alloys. The original goal of undercooling the liquid metal well below the liquidus to the peritectic temperature during containerless free to form primarily NiAl3 was achieved. The microstructures were interesting from another point of view. The microstructure from small diameter samples is greatly refined. Small dendrite arm spacings such as these could greatly facilitate the annealing and solid state transformation of the alloy to nearly 10% NiAl3 by reducing the distance over which diffusion needs to occur. This could minimize annealing time and might make it economically feasible to produce NiAl3 alloy.
    Keywords: METALLIC MATERIALS
    Type: NASA. Marshall Space Flight Center 2nd Symp. on Space Industrialization; p 293-303
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  • 30
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    Directional solidification of flake and nodular cast iron during KC-135 low-g maneuvers (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Alloys solidified in a low-gravity environment can, due to the elimination of sedimentation and convection, form unique and often desirable microstructures. One method of studying the effects of low-gravity (low-g) on alloy solidification was the use of the NASA KC-135 aircraft flying repetitive low-g maneuvers. Each maneuver gives from 20 to 30 seconds of low-g which is between about 0.1 and 0.001 gravity. A directional solidification furnace was used to study the behavior of off eutectic composition case irons in a low-g environment. The solidification interface of hypereutectic flake and spheroidal graphite case irons was slowly advanced through a rod sample, 5 mm in diameter. Controlled solidification was continued through a number of aircraft parabolas. The known solidification rate of the sample was then correlated with accelerometer data to determine the gravity level during solidification for any location of the sample. The thermal gradient and solidification rate were controlled independently. Samples run on the KC-135 aircraft exhibited bands of coarser graphite or of larger nodules usually corresponding to the regions solidified under low-g. Samples containing high phosphorous (used in order to determine the eutectic cell) exhibited larger eutectic cells in the low-g zone, followed by a band of coarser graphite.
    Keywords: METALLIC MATERIALS
    Type: 2nd Symp. on Space Industrialization; p 275-291
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  • 31
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    Status of Understanding for Bearing Materials (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The structural materials and potential failure modes for high technology aircraft gas turbine bearings are reviewed. Among the failure modes discussed for iron-base through-hardened bearing materials are fatigue, surface distress, and corrosion. It is shown that the sub-surface initiated rolling-contact fatigue failure mode is reasonably well understood and in most cases can be controlled by proper material selection and design. Current bearing materials provide long life and high reliability in existing applications. A new generation of materials are being developed which will provide improved fracture toughness, better corrosion resistance, and a further extension of bearing fatigue life. Bearing problems due to surface distress, caused by a variety of surface and near surface anomalies, are less well understood. This area will require the implementation of an interdisciplinary effort to improve the level of understanding of metallic surface-lubricant reactions and interactions.
    Keywords: METALLIC MATERIALS
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 773-794
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  • 32
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    The Strength of the Metal. Aluminum Oxide Interface (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The strength of the interface between metals and aluminum oxide is an important factor in the successful operation of devices found throughout modern technology. One finds the interface in machine tools, jet engines, and microelectronic integrated circuits. The strength of the interface, however, should be strong or weak depending on the application. The diverse technological demands have led to some general ideas concerning the origin of the interfacial strength, and have stimulated fundamental research on the problem. Present status of our understanding of the source of the strength of the metal - aluminum oxide interface in terms of interatomic bonds are reviewed. Some future directions for research are suggested.
    Keywords: METALLIC MATERIALS
    Type: Tribology in the 80's. Vol. 1; p 165-175
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  • 33
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    Metallic Adhesion and Bonding (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Although metallic adhesion has played a central part in much tribological speculation, few quantitative theoretical calculations are available. This is in part because of the difficulties involved in such calculations and in part because the theoretical physics community is not particularly involved with tribology. The calculations currently involved in metallic adhesion are summarized and shown that these can be generalized into a scaled universal relationship. Relationships exist to other types of covalent bonding, such as cohesive, chemisorptive, and molecular bonding. A simple relationship between surface energy and cohesive energy is offered.
    Keywords: METALLIC MATERIALS
    Type: Tribology in the 80's. Vol. 1; p 143-162
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  • 34
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    Performance of thermal barrier coatings in high heat flux environments (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8 percent Y203 specimens survived 3000 of the 0.5 sec cycles with failing. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 2 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12 percent Y2O3 or ZrO2-20 percent Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.
    Keywords: METALLIC MATERIALS
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  • 35
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    Mechanical-contact-induced transformation from the amorphous to the partially crystalline state in metallic glass (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Friction and wear tests were conducted with 3.2- and 6.4-millimeter-diameter aluminum oxide spheres sliding, in reciprocating motion, on a Fe67Co18B14Si1 metallic foil. Crystallites with a size range of 10 to 150 nanometers were produced on the wear surface of the amorphous alloy. A strong interaction between transition metals and metalloids such as silicon and boron results in strong segregation during repeated sliding, provides preferential transition metal-metalloid clustering in the amorphous alloy, and subsequently produces the diffused honeycomb structure formed by dark grey bands and primary crystals, that is, alpha-Fe in the matrix. Large plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminum oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris, and/or powdery-whiskery oxide debris.
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  • 36
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    Rapid solidification via melt spinning - Equipment and techniques (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: One of the simpler methods available to accomplish rapid solidification processing is free jet melt spinning. With only a modest expenditure of time, effort, and capital, an apparatus suitable for preliminary experimentation can be assembled. Wheel and crucible materials, process atmospheres, crucible design, heating methods, and process parameters and their relationship to melt composition are described. Practical solutions to processing problems, based on 'hands-on' experience, are offered. Alloys with melting points up to 3000 F have been rapidly solidified using the techniques described.
    Keywords: METALLIC MATERIALS
    Type: Journal of Metals (ISSN 0148-6608); 36; 41-45
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  • 37
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    Effects of processing and microstructure on the fatigue behaviour of the nickel-base superalloy Rene95 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Forms of the nickel-base superalloy Rene95 produced by three processing methods were evaluated in tensile, low cycle fatigue and fatigue crack propagation tests at 540 and 650 C. Two powder-metallurgy (PM) forms, hot-isostatically-pressed and extruded-and-forged, and a conventionally cast-and-wrought form were all given the same heat treatment. The extruded-and-forged form showed superior fatigue life in low strain range tests though the two PM forms exhibited nearly identical mechanical behavior in all other respects. Further, this life difference could not be explained by significant differences in the types, sizes or shapes of the defects initiating failure. The cast-and-wrought Rene95, however, had lower strength, ductility and fatigue life, but higher fatigue crack propagation resistance because of a larger grain size. It did not exhibit the environmentally-assisted intergranular mode of propagation which occurs in PM Rene95 and other fine-grained superalloys at these test temperatures and frequencies.
    Keywords: METALLIC MATERIALS
    Type: International Journal of Fatigue (ISSN 0142-1123); 6; 189-193
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  • 38
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    A simple application of the Bailey-Orowan creep model to Fe-39.8 at. pct Al and gamma/gamma prime - alpha (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The results of a study to determine the recovery rates and work-hardening coefficients for creep from constant cross-head speed compressive tests are presented. Stressing and straining rates are computed from measured time-load curves obtained from compression testing between 1200 and 1400 K of several B2 crystal structure Fe-39.8 Al intermetallic materials and the directionally solidified eutectic alloy gamma/gamma prime alpha. These quantities are then fitted to the universal form of the Bailey-Orowan equation for creep. The recovery rates were found to be functions of nominal strain rate, stress, and temperature, while the hardening coefficients were dependent only on temperature. While the work-hardening coefficient for gamma/gamma prime - alpha was about 0.05 of the elastic modulus, the work-hardening coefficients for Fe-39.8 at. pct Al were less than 0.002 of the modulus.
    Keywords: METALLIC MATERIALS
    Type: Journal of Materials Science (ISSN 0022-2461); 19; 509-517
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  • 39
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    Surface protection (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The surface protection subproject consists of three major thrusts: airfoil deposition model; metallic coating life prediction; and thermal barrier coating (TBC) life prediction. The time frame for each of these thrusts and the expected outputs are presented. Further details are given for each thrust such as specific element schedules and the status of performance; in-house, via grant, or via contract.
    Keywords: METALLIC MATERIALS
    Type: Turbine Engine Hot Section Technology, 1984; 10 p
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  • 40
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    Low-gravity solidification of cast iron and space technology applications (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two types of analyses relating to cast iron solidification were conducted. A theoretical analysis using a computer to predict the cooling versus time relationship throughout the test specimen was performed. Tests were also conducted in a ground-based laboratory to generate a cooling time curve for cast iron. In addition, cast iron was cooled through the solidification period on a KC-135 and an F-104 aircraft while these aircraft were going through a period of low gravity. Future subjects for low gravity tests are enumerated.
    Keywords: METALLIC MATERIALS
    Type: NASA. Marshall Space Flight Center 2nd Symp. on Space Industrialization; p 75-81
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  • 41
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    Understanding the roles of the strategic element cobalt in nickel base superalloys (1984)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Research progress in understanding the effects of cobalt and some possible substitute on microstructure, mechanical properties, and environmental resistance of turbine alloys is discussed. The United States imports over 90 percent of its cobalt, chromium, tantalum and columbium, all key elements in high temperature nickel base superalloys for aircraft gas turbine disks and airfoils. NASA, through joint government/industry/university teams, undertook a long range research program aimed at reducing or eliminating these strategic elements by examining their basic roles in superalloys and identifying viable substitutes.
    Keywords: METALLIC MATERIALS
    Type: AGARD Mater. Substitution and Recycling; 15 p
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  • 42
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    On the use of marker loads and replicas for measuring growth rates for small cracks (1984)
    In:  Other Sources
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    Publication Date: 2018-12-01
    Description: The initiation and growth of small cracks (5-500 microns) from edge notches in 2024-T3 aluminum alloy sheets were studied under constant-amplitude loading. Two methods were used to measure crack shape and size. In the first method, striation marker bands were periodically formed along the crack front by interrupting the constant-amplitude loading by either an elevated R-ratio load sequence, or by an overload sequence. In each case the marker loading was selected so as to have minimal influence on the growth rate under the primary loading. In the second method, the surface crack length was monitored by taking surface replicas at regular intervals. The marker band techniques did not provide reliable crack length and crack shape information for cracks smaller than 2 mm. The replica technique provided accurate information for surface crack length at all crack lengths, and fracture tests on specimens with small cracks provided crack-shape information.
    Keywords: METALLIC MATERIALS
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  • 43
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    Effects of surface chemistry on hot corrosion life (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Hot corrosion life prediction methodology based on a combination of laboratory test data and field service turbine components, which show evidence of hot corrosion, were examined. Components were evaluated by optical metallography, scanning electron microscopy (SEM), and electron micropulse (EMP) examination.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Turbine Engine Hote Section Technology, 1984; 14 p
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  • 44
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    Experimental verification of vapor deposition model in Mach 0.3 burner rigs (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A comprehensive theoretical framework of deposition from combustion gases was developed covering the spectrum of various mass delivery mechanisms including vapor, thermophoretically enhanced small particle, and inertially impacting large particle deposition. Rational yet simple correlations were provided to facilitate engineering surface arrival rate predictions. Experimental verification of the deposition theory was validated using burner rigs. Toward this end, a Mach 0.3 burner rig apparatus was designed to measure deposition rates from salt-seeded combustion gases on an internally cooled cylindrical collector.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Turbine Engine Hot Section Technology, 1984; 13 p
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  • 45
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    Failure analysis of plasma-sprayed thermal barrier coatings (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Thermally induced failure processes of plasma-sprayed thermal barrier coatings are examined. Cracking processes give rise to noise which was monitored by acoustic emission (AE) techniques. The sequential failure of coatings was examined from samples which were thermally cycled. Coatings of yttria-stabilized zirconia with and without a NiCrAlZr bond coat were plasma-sprayed onto U700 alloy rod. In some cases the substrate was intentionally overheated during deposition of the thermal protection system to check how this process variable influenced the AE response of the specimen. In this way a qualitative appraisal of how process variables affect coating integrity could be discerned in terms of cracking behavior. Results from up to seven consecutive thermal cycles are reported here. Coating failure was observed in all cases. Failure of the thermal protection system is progressive, since cracking and crack growth were observed prior to ultimate failure. Thus castastrophic failure occurs at some stage when there is a transformation from the microcrack to a macrocrack network.
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  • 46
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    Modeling degradation and failure of Ni-Cr-Al overlay coatings (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Degradation of a Ni-16Cr-25Al-0.06Zr overlay coating on a Ni-22Cr substrate was examined after oxidation accompanied by thermal cycling. Concentration/distance profiles were measured in the coating and substrate after various one-hour cycles at 1150 C. A numerical model was developed to simulate coating degradation by simultaneous oxidation and coating/substrate interdiffusion. The validity of the model was confirmed by comparison of predicted and measured concentration/distance profiles. The ability of the model to identify critical system parameters was demonstrated for the case of initial Al and Cr content of the coating and substrate.
    Keywords: METALLIC MATERIALS
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  • 47
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    Structure and recalescence behavior of undercooled nickel-tin alloys (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The effects of undercooling on the thermal behavior and structure of Ni-Sn alloys are investigated. Hypoeutectic (Ni-25 wt pct Sn) and eutectic (Ni-32.5 wt pct Sn) compositions of the Ni-Sn alloy were undercooled using a levitation melting with glass encasement technique, and the recalescence of these alloys was measured using a high speed temperature sensing device and a digital oscilloscope. It is observed that in both samples the total solidification and recalescence times decrease with increasing undercooling; the volume fraction of normal lamellar eutectic decreases with increasing undercooling; and in the hypoeutectic sample, the morphology of the primary phase changes from dendritic to spherical with increasing undercooling.
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  • 48
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    A simple method of obtaining concentration depth-profiles from X-ray diffraction (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The construction of composition profiles from X-ray intensity bands was investigated. The intensity band-to-composition profile transformation utilizes a solution which can be easily evaluated. The technique can be applied to thin films and thick speciments for which the variation of lattice parameters, linear absorption coefficient, and reflectivity with composition are known. A deconvolution scheme with corrections for the instrumental broadening and ak-alfadoublet is discussed.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-176262 , NAS 1.26:176262 , TMS-PAPER-F8415
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  • 49
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    Utilizing various test methods to study the stress corrosion behavior of Al-Li-Cu alloys (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Recently, much attention has been given to aluminum-lithium alloys because of rather substantial specific-strength and specific-stiffness advantages offered over commercial 2000and 7000-series aluminum alloys. An obstacle to Al-Li alloy development has been inherent limited ductility. In order to obtain a more refined microstructure, powder metallurgy (P/M) has been employed in alloy development programs. As stress corrosion (SC) of high-strength aluminum alloys has been a major problem in the aircraft industry, the possibility of an employment of Al-Li alloys has been considered, taking into account a use of Al-Li-Cu alloys. Attention is given to a research program concerned with the evaluation of the relative SC resistance of two P/M processed Al-Li-Cu alloys. The behavior of the alloys, with and without an addition of magnesium, was studied with the aid of three test methods. The susceptibility to SC was found to depend on the microstructure of the alloys.
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  • 50
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    Microstructures and properties of rapidly solidified alloys (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The microstructure and properties of rapidly solidified aluminum alloys were researched. The effects of powder and flake chemistry and morphology and alternative consolidation processing parameters are being conducted. Samples of the powders being utilized were obtained for comprehensive metallurgical characterization. Seven aluminum alloys in the form of thin foils were studied by a variety of techniques including optical metallography, scanning electron microscope, and transmission electron microscope. Details of the microstructural characteristics are presented along with a discussion of the solidification process. A better understanding of the microstructure of the rapidly solidified aluminum alloys prepared by a variety of techniques such as roller quenching, the vacuum atomized procedure, ultrasonically atomized in inert atmospheres, and atomized in flue gas was provided.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-172377 , NAS 1.26:172377
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  • 51
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    Low cycle fatigue behavior of conventionally cast MAR-M 200 AT 1000 deg C (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The low cycle fatigue behavior of the nickel-based superalloy MAR-M 200 in conventionally cast form was studied at 1000 C. Continuous cycling tests, without hold times, were conducted with inelastic strain ranges of from 0.04 to 0.33 percent. Tests were also conducted which included a hold time at peak strain in either tension or compression. For the conditions studied, it was determined that imposition of hold times did not significantly affect the fatigue life. Also, for continuous cycling tests, increasing or decreasing the cycle frequency did not affect life. Metallographic analysis revealed that the most significant damage mechanism involved environmentally assisted intergranular crack initiation and propagation, regardless of the cycle type. Changes in the gamma morphology (rafting and rod formation) were observed, but did not significantly affect the failure.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83769 , E-2260 , NAS 1.15:83769 , USAAVSCOM-TR-84-C-16 , AD-A149178
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  • 52
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    Overlay metallic-cermet alloy coating systems (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A substrate, such as a turbine blade, vane, or the like, which is subjected to high temperature use is coated with a base coating of an oxide dispersed, metallic alloy (cermet). A top coating of an oxidation, hot corrosion, erosion resistant alloy of nickel, cobalt, or iron is then deposited on the base coating. A heat treatment is used to improve the bonding. The base coating serves as an inhibitor to interdiffusion between the protective top coating and the substrate. Otherwise, the protective top coating would rapidly interact detrimentally with the substrate and degrade by spalling of the protective oxides formed on the outer surface at elevated temperatures.
    Keywords: METALLIC MATERIALS
    Type: NAS 1.71:LEW-13639-1
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  • 53
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    Empirical relations for cavitation and liquid impingement erosion processes (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A unified power-law relationship between average erosion rate and cumulative erosion is presented. Extensive data analyses from venturi, magnetostriction (stationary and oscillating specimens), liquid drop, and jet impact devices appear to conform to this relation. A normalization technique using cavitation and liquid impingement erosion data is also presented to facilitate prediction. Attempts are made to understand the relationship between the coefficients in the power-law relationships and the material properties.
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2339 , E-1872 , NAS 1.60:2339
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  • 54
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    Evaluation of the effect of crack closure on fatigue crack growth of simulated short cracks (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A test program was performed to determine the influence of crack closure on fatigue crack growth (FCG) rates of short cracks. By use of the standard compact tension specimen, test procedures were devised to evaluate closure loads in the wake of the crack behind its tip. The first procedure determined the magnitude of crack closure as a function of the fatigued crack wave by incrementally removing the contacting wake surfaces and measuring closure load at each increment. The second procedure used a low-high loading sequence to simulate short crack behavior. Based on the results, it was concluded that crack closure is not the major reason for the more rapid growth of short cracks as compared to long crack growth.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83778 , E-2063 , NAS 1.15:83778
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  • 55
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    High-Temperature Cyclic Oxidation Data, Volume 1 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This first in a series of cyclic oxidation handbooks contains specific-weight-change-versus-time data and X-ray diffraction results derived from high-temperature cyclic tests on high-temperature, high-strength nickel-base gamma/gamma' and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83665 , E-1499 , NAS 1.15:83665
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  • 56
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    Development of improved low-strain creep strength in Cabot alloy R-41 sheet (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The feasibility of improving the low-strain creep properties of a thin gauge nickel base sheet alloy through modified heat treatment or through development of a preferred crystal-lographic texture was investigated. The basic approach taken to improve the creep strength of the material by heat treatment was to increase grain size by raising the solution treatment temperature for the alloy to the range of 1420 K to 1475 K (2100 F to 2200 F). The key technical issue involved was maintenance of adequate tensile ductility following the solutioning of M6C primary carbides during the higher temperature solution treatment. The approach to improve creep properties by developing a sheet texture involved varying both annealing temperatures and the amount of prior cold work. Results identified a heat treatment for alloy R-14 sheet which yields a substantial creep-life advantage at temperatures above 1090 K (1500 F) when compared with material given the standard heat treatment. At the same time, this treatment provides reasonable tensile ductility over the entire temperature range of interest. The mechanical properties of the material given the new heat treatment are compared with those for material given the standard heat treatment. Attempts to improve creep strength by developing a sheet texture were unsuccessful.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-172392 , NAS 1.26:172392 , REPT-11816
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  • 57
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    Flight service evaluation of two aluminum-brazed titanium spoilers (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The long-term service evaluation of two aluminum-brazed titanium (ABTi) honeycomb flight spoilers was concluded. The two spoilers had about 7.5 years of commercial flight experience on All Nippon Airways Model 737 aircraft. All Nippon Airways was selected because Japan has one of the most severe marine-industrial environments in the world. The results indicated that both flight spoilers still had the same load-carrying capability as when they were originally installed. No direct evidence of any corrosion was observed on either spoiler. Another significant accomplishment of this effort was the development of a braze design for efficiently distributing point loads from the fittings and skin into the honeycomb core.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-172371 , NAS 1.26:172371 , D6-52046
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  • 58
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    Grain-refining heat treatments to improve cryogenic toughness of high-strength steels (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The development of two high Reynolds number wind tunnels at NASA Langley Research Center which operate at cryogenic temperatures with high dynamic pressures has imposed severe requirements on materials for model construction. Existing commercial high strength steels lack sufficient toughness to permit their safe use at temperatures approaching that of liquid nitrogen (-320 F). Therefore, a program to improve the cryogenic toughness of commercial high strength steels was conducted. Significant improvement in the cryogenic toughness of commercial high strength martensitic and maraging steels was demonstrated through the use of grain refining heat treatments. Charpy impact strength at -320 F was increased by 50 to 180 percent for the various alloys without significant loss in tensile strength. The grain sizes of the 9 percent Ni-Co alloys and 200 grade maraging steels were reduced to 1/10 of the original size or smaller, with the added benefit of improved machinability. This grain refining technique should permit these alloys with ultimate strengths of 220 to 270 ksi to receive consideration for cryogenic service.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-85816 , L-15693 , NAS 1.15:85816
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  • 59
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    Erosion of iron-chromium alloys by glass particles (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping.
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2354 , E-1615 , NAS 1.60:2354
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  • 60
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    Fastener load tests and retention systems tests for cryogenic wind-tunnel models (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A-286 stainless steel screws were tested to determine the tensile load capability and failure mode of various screw sizes and types at both cryogenic and room temperature. Additionally, five fastener retention systems were tested by using A-286 screws with specimens made from the primary metallic alloys that are currently used for cryogenic models. The locking system effectiveness was examined by simple no-load cycling to cryogenic temperatures (-275 F) as well as by dynamic and static loading at cryogenic temperatures. In general, most systems were found to be effective retention devices. There are some differences between the various devices with respect to ease of application, cleanup, and reuse. Results of tests at -275 F imply that the cold temperatures act to improve screw retention. The improved retention is probably the result of differential thermal contraction and/or increased friction (thread-binding effects). The data provided are useful in selecting screw sizes, types, and locking devices for model systems to be tested in cryogenic wind tunnels.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-85805 , L-15751 , NAS 1.15:85805
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  • 61
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    Creep-rupture behavior of candidate Stirling engine iron supperalloys in high-pressure hydrogen. Volume 2: Hydrogen creep-rupture behavior (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The creep rupture behavior of nine iron base and one cobalt base candidate Stirling engine alloys is evaluated. Rupture life, minimum creep rate, and time to 1% strain data are analyzed. The 3500 h rupture life stress and stress to obtain 1% strain in 3500 h are also estimated.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174705 , NAS 1.26:174705 , IITRI-M06116-15
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  • 62
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    Oxidation and corrosion resistance of candidate Stirling engine heater-head-tube alloys (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Sixteen candidate iron base Stirling engine heater head tube alloys are evaluated in a diesel fuel fired simulator materials test rig to determine their oxidation and corrosion resistance. Sheet specimens are tested at 820 C for 3500 hr in 5 hr heating cycles. Specific weight change data and an attack parameter are used to categorize the alloys into four groups; 10 alloys show excellent for good oxidation and corrosion resistance and six alloys exhibit poor or catastrophic resistance. Metallographic, X-ray, and electron microprobe analyses aid in further characterizing the oxidation and corrosion behavior of the alloys. Alloy compositions, expecially the reactive elements aluminum, titanium, and chromium, play a major role in the excellent oxidation and corrosion behavior of the alloys. The best oxidation resistance is associated with the formation of an iron nickel aluminum outer oxide scale, an intermediate oxide scale rich in chromium and titanium, and an aluminum outer oxide scale adjacent to the metallic substrate, which exhibits a zone of internal oxidation of aluminum and to some extent titanium.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83609 , DOE/NASA/51040-53 , E-2028 , NAS 1.15:83609
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  • 63
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    Development of carbon slurry fuels for transportation (hybrid fuels, phase 2) (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Slurry fuels of various forms of solids in diesel fuel are developed and evaluated for their relative potential as fuel for diesel engines. Thirteen test fuels with different solids concentrations are formulated using eight different materials. A variety of properties are examined including ash content, sulfur content, particle size distribution, and rheological properties. Attempts are made to determine the effects of these variations on these fuel properties on injection, atomization, and combustion processes. The slurries are also tested in a single cylinder CLR engine in both direct injection and prechamber configurations. The data includes the normal performance parameters as well as heat release rates and emissions. The slurries perform very much like the baseline fuel. The combustion data indicate that a large fraction (90 percent or more) of the solids are burning in the engine. It appears that the prechamber engine configuration is more tolerant of the slurries than the direct injection configuration.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174659 , DOE/NASA/0263-1 , NAS 1.26:174659 , SWRI-6948
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  • 64
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    Chemical mechanisms and reaction rates for the initiation of hot corrosion of IN-738 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Sodium-sulfate-induced hot corrosion of preoxidized IN-738 was studied at 975 C with special emphasis placed on the processes occurring during the long induction period. Thermogravimetric tests were run for predetermined periods of time, and then one set of specimens was washed with water. Chemical analysis of the wash solutions yielded information about water soluble metal salts and residual sulfate. A second set of samples was cross sectioned dry and polished in a nonaqueous medium. Element distributions within the oxide scale were obtained from electron microprobe X-ray micrographs. Evolution of SO was monitored throughout the thermogravimetric tests. Kinetic rate studies were performed for several pertinent processes; appropriate rate constants were obtained from the following chemical reactions: Cr2O3 + 2 Na2SO4(1) + 3/2 O2 yields 2 Na2CrO4(1) + 2 SO3(g)n TiO2 + Na2SO4(1) yields Na2O(TiO2)n + SO3(g)n TiO2 + Na2CrO4(1) yields Na2O(TiO2)n + CrO3(g).
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2319 , E-1847 , NAS 1.60:2319
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  • 65
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    In-situ measurements of alloy oxidation/corrosion/erosion using a video camera and proximity sensor with microcomputer control (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Two noncontacting and nondestructive, remotely controlled methods of measuring the progress of oxidation/corrosion/erosion of metal alloys, exposed to flame test conditions, are described. The external diameter of a sample under test in a flame was measured by a video camera width measurement system. An eddy current proximity probe system, for measurements outside of the flame, was also developed and tested. The two techniques were applied to the measurement of the oxidation of 304 stainless steel at 910 C using a Mach 0.3 flame. The eddy current probe system yielded a recession rate of 0.41 mils diameter loss per hour and the video system gave 0.27.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83673 , E-2117 , NAS 1.15:83673
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  • 66
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    Coating with overlay metallic-cermet alloy systems (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A base layer of an oxide dispersed, metallic alloy (cermet) is arc plasma sprayed onto a substrate, such as a turbine blade, vane, or the like, which is subjected to high temperature use. A top layer of an oxidation, hot corrosion, erosion resistant alloy of nickel, cobalt, or iron is then arc plasma sprayed onto the base layer. A heat treatment is used to improve the bonding. The base layer serves as an inhibitor to interdiffusion between the protective top layer and the substrate. Otherwise, the 10 protective top layer would rapidly interact detrimentally with the substrate and degrade by spalling of the protective oxides formed on the outer surface at elevated temperatures.
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  • 67
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    Solubility of hydrogen in metals and its effect of pore-formation and embrittlement (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effect of alloying elements on hydrogen solubility were determined by evaluating solubility equations and interaction coefficients. The solubility of dry hydrogen at one atmosphere was investigated in liquid aluminum, Al-Ti, Al-Si, Al-Fe, liquid gold, Au-Cu, and Au-Pd. The design of rapid heating and high pressure casting furnaces used in meta foam experiments is discussed as well as the mechanism of precipitation of pores in melts, and the effect of hydrogen on the shrinkage porosity of Al-Cu and Al-Si alloys. Hydrogen embrittlement in iron base alloys is also examined.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-173399 , NAS 1.26:173399
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  • 68
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    Analysis and calculation of macrosegregation in a casting ingot, exhibits C and E (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer model which describes the solidification of a binary metal alloy in an insulated rectangular mold with a temperature gradient is presented. A numerical technique, applicable to a broad class of moving boundary problems, was implemented therein. The solidification model described is used to calculate the macrosegregation within the solidified casting by coupling the equations for liquid flow in the solid/liquid or mushy zone with the energy equation for heat flow throughout the ingot and thermal convection in the bulk liquid portion. The rate of development of the solid can be automatically calculated by the model. Numerical analysis of such solidification parameters as enthalpy and boundary layer flow is displayed. On-line user interface and software documentation are presented.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-171030 , NAS 1.26:171030 , REPT-84HV001
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  • 69
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    Review of the Effects of Microstructure on Fatigue in Aluminum Alloys (1984)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Literature survey was conducted to determine the effects of different microstructural features and different load histories on fatigue crack initiation and propagation of aluminum alloys. Comparison of microstructure and monotonic and cyclic properties between powder metallurgy (P/M) and ingot metallurgy (I/M) alloys is presented. The two alloys that are representative of each process on which the comparison is focused are X7091 and 7050. Included is a detailed description of the microstructure produced through the P/M and I/M proesses. The effect of each pertinent microstructural feature on monotonic and cyclic properties, such as yield strength, toughness, crack initiation and propagation is discussed. Also discussed are the proposed mechanisms for crack initiation and propagation, as well as the effects of aggressive environments on these cyclic properties. The effects of variable amplitude loadin on fatigue crack propagation and the various models proposed to predict load interaction effects are discussed.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83626 , E-2061 , NAS 1.15:83626
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  • 70
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    Evaluation of a non-catalytic coating for metallic TPS (1984)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A commercially available ceramic coating was evaluated for application to metallic heat shields for Shuttle-type entry vehicles. Coated Inconel 617 specimens were subjected to thermal shock cycles, surface emittances were measured, and surface equilibrium temperatures were measured for coated and oxidized specimens exposed to an arc-tunnel environment. The coating adhered very well to the metal and appeared to be very non-catalytic.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-85745 , NAS 1.15:85745
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  • 71
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    Materials for Advanced Turbine Engines (MATE): Project 3: Design, fabrication and evaluation of an oxide dispersion strengthened sheet alloy combustor liner, volume 1 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The suitability of wrought oxide dispersion strengthened (ODS) superalloy sheet for gas turbine engine combustor applications was evaluated. Incoloy MA 956 (FeCrAl base) and Haynes Developmental Alloy (HDA) 8077 (NiCrAl base) were evaluated. Preliminary tests showed both alloys to be potentially viable combustor materials, with neither alloy exhibiting a significant advantage over the other. Both alloys demonstrated a +167C (300 F) advantage of creep and oxidation resistance with no improvement in thermal fatigue capability compared to a current generation combustor alloy (Hastelloy X). MA956 alloy was selected for further demonstration because it exhibited better manufacturing reproducibility than HDA8077. Additional property tests were conducted on MA956. To accommodate the limited thermal fatigue capability of ODS alloys, two segmented, mechanically attached, low strain ODS combustor design concepts having predicted fatigue lives or = 10,000 engine cycles were identified. One of these was a relatively conventional louvered geometry, while the other involved a transpiration cooled configuration. A series of 10,000 cycle combustor rig tests on subscale MA956 and Hastelloy X combustor components showed no cracking, thereby confirming the beneficial effect of the segmented design on thermal fatigue capability. These tests also confirmed the superior oxidation and thermal distortion resistance of the ODS alloy. A hybrid PW2037 inner burner liner containing MA956 and Hastelloy X components was designed and constructed.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174691 , NAS 1.26:174691 , PWA-5574-175-VOL-1
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  • 72
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    Effects of alloy composition on cyclic flame hot-corrosion attack of cast nickel-base superalloys at 900 deg C (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effects of Cr, Al, Ti, Mo, Ta, Nb, and W content on the hot corrosion of nickel base alloys were investigated. The alloys were tested in a Mach 0.3 flame with 0.5 ppmw sodium at a temperature of 900 C. One nondestructive and three destructive tests were conducted. The best corrosion resistance was achieved when the Cr content was 12 wt %. However, some lower-Cr-content alloys ( 10 wt%) exhibited reasonable resistance provided that the Al content alloys ( 10 wt %) exhibited reasonable resistance provided that the Al content was 2.5 wt % and the Ti content was Aa wt %. The effect of W, Ta, Mo, and Nb contents on the hot-corrosion resistance varied depending on the Al and Ti contents. Several commercial alloy compositions were also tested and the corrosion attack was measured. Predicted attack was calculated for these alloys from derived regression equations and was in reasonable agreement with that experimentally measured. The regression equations were derived from measurements made on alloys in a one-quarter replicate of a 2(7) statistical design alloy composition experiment. These regression equations represent a simple linear model and are only a very preliminary analysis of the data needed to provide insights into the experimental method.
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2338 , E-2009 , NAS 1.60:2338
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  • 73
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    Advanced powder metallurgy aluminum alloys via rapid solidification technology (1984)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Aluminum alloys containing 10 to 11.5 wt. pct. of iron and 1.5 to 3 wt. pct. of chromium using the technique of rapid solidification powder metallurgy were studied. Alloys were prepared as thin ribbons (.002 inch thick) rapidly solidified at uniform rate of 10(6) C/second by the melt spinning process. The melt spun ribbons were pulverized into powders (-60 to 400 mesh) by a rotating hammer mill. The powders were consolidated by hot extrusion at a high reduction ratio of 50:1. The powder extrusion temperature was varied to determine the range of desirable processing conditions necessary to yield useful properties. Powders and consolidated alloys were characterized by SEM and optical metallography. The consolidated alloys were evaluated for (1) thermal stability, (2) tensile properties in the range, room temperature to 450 F, and (3) notch toughness in the range, room temperature to 450 F.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-172343 , NAS 1.26:172343
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  • 74
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    Creep-rupture behavior of candidate Stirling engine alloys after long-term aging at 760 deg C in low-pressure hydrogen (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Nine candidate Stirling automotive engine alloys were aged at 760 C for 3500 hr in low pressure hydrogen or argon to determine the resulting effects on mechanical behavior. Candidate heater head tube alloys were CG-27, W545, 12RN72, INCONEL-718, and HS-188 while candidate cast cylinder-regenerator housing alloys were SA-F11, CRM-6D, XF-818, and HS-31. Aging per se is detrimental to the creep rupture and tensile strengths of the iron base alloys. The presence of hydrogen does not significantly contribute to strength degradation. Based percent highway driving cycle; CG-27 has adequate 3500 hr - 870 C creep rupture strength and SA-Fll, CRM-6D, and XF-818 have adequate 3500 hr - 775 C creep rupture strength.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83676 , DOE/NASA/51040-55 , E-2124 , NAS 1.15:83676
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  • 75
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    Fracture temperature and flaw growth in nitronic 40 at cryogenic temperatures (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The fracture resistance and fatigue response of Armco Nitronic 40 austenitic stainless steel were evaluated under cryogenic conditions. Tensile, fracture toughness and fatigue crack growth properties were measured at -275 F. The tensile yield strength was approximately 120 ksi and the fracture toughness was estimated to be 350 ksi-in /2 on the basis of fracture toughness measurements. Testing was conducted to evaluate the behavior of a simulated section of the wing of the Pathfinder 1 model subject to a load and temperature history typical of that for testing in the National Transonic Facility. The wing section model incorporated a proposed brazing technique for pressure-transducer attachment. The simulated wing section performed satisfactorily at stress levels of nearly 60 percent of the material yield strength. The brazing technique proved to be an effective method of transducer attachment under conditions of high stress levels and large temperature excursions.
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2312 , L-15722 , NAS 1.60:2312
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  • 76
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    Method of making a light weight battery plaque (1984)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A nickel plaque which may be coated with a suitable metal or compound to make an electrode for a fuel cell or battery is fabricated by directing nickel sensitizer, catalyst and plating solutions through a porous plastic substrate in the order named and at prescribed temperatures and flow rates. A boride compound dissolved in the plating solution decreases the electrical resistance of the plaque. Certain substrates may require treatment in an alkali solution to dissolve filler materials thereby increasing porosity to a required 65%.
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  • 77
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    A study of the solidification parameters influencing structures and properties in MAR-M246(Hf) (1984)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The nickel-base superalloy MAR-246(Hf) was studied to determine the factors affecting basic morphology and fatigue properties. Of particular interest was the degradation of fatigue properties with deviation from the 001 growth orientation. Examination of directionally solidified samples showed a dependence of carbide shape and interdentritic segregation on growth rate. Heat treatment studies focused on the gamma prime structure, determining that it reaches maximum growth after twenty-four hours but its size and stability depends on the temperature of the treatment. Fatigue test specimens were oriented crystallographically in the failed and unfailed regions and found to have rotated their orientation during the testing if they were located a significant distance from 001. This would place increased strain on the crystal and precipitate early failure.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-82569 , NAS 1.15:82569
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  • 78
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    Literature survey on oxidations and fatigue lives at elevated temperatures (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Nickel-base superalloys are the most complex and the most widely used for high temperature applications such as aircraft engine components. The desirable properties of nickel-base superalloys at high temperatures are tensile strength, thermomechanical fatigue resistance, low thermal expansion, as well as oxidation resistance. At elevated temperature, fatigue cracks are often initiated by grain boundary oxidation, and fatigue cracks often propagate along grain boundaries, where the oxidation rate is higher. Oxidation takes place at the interface between metal and gas. Properties of the metal substrate, the gaseous environment, as well as the oxides formed all interact to make the oxidation behavior of nickel-base superalloys extremely complicated. The important topics include general oxidation, selective oxidation, internal oxidation, grain boundary oxidation, multilayer oxide structure, accelerated oxidation under stress, stress-generation during oxidation, composition and substrate microstructural changes due to prolonged oxidation, fatigue crack initiation at oxidized grain boundaries and the oxidation accelerated fatigue crack propagation along grain boundaries.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174639 , NAS 1.26:174639
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  • 79
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    The role of cobalt on the creep of Waspaloy (1984)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Cobalt was systematically replaced with nickel in Waspaloy (which normally contains 13% Co) to determine the effects of cobalt on the creep behavior of this alloy. Effects of cobalt were found to be minimal on tensile strengths and microstructure. The creep resistance and the stress rupture resistance determined in the range from 704 to 760 C (1300 to 1400 C) were found to decrease as cobalt was removed from the standard alloy at all stresses and temperatures. Roughly a ten-fold drop in rupture life and a corresponding increase in minimum creep rate were found under all test conditions. Both the apparent creep activation energy and the matrix contribution to creep resistance were found to increase with cobalt. These creep effects are attributed to cobalt lowering the stacking fault energy of the alloy matrix. The creep resistance loss due to the removal of cobalt is shown to be restored by slightly increasing the gamma' volume fraction. Results are compared to a previous study on Udimet 700, a higher strength, higher gamma' volume fraction alloy with similar phase chemistry, in which cobalt did not affect creep resistance. An explanation for this difference in behavior based on interparticle spacing and cross-slip is presented.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174628 , NAS 1.26:174628
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  • 80
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    Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2278 , E-1854 , NAS 1.60:2278
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  • 81
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    Application of induction coil measurements to the study of superalloy hot corrosion and oxidation (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The assessment of the degree of hot corrosion attack on nickel based alloys is a difficult task, especially when the definition specifies that it must be in terms of metal consumed and even more difficult if the measurement must be nondestructive. The inductance of a solenoid coil responds to changes in volume of fill and composition of metal cores, therefore, it may be used for nondestructive measurement of hot corrosion. The hot corrosion of U700 was studied at 900 C in a Mach 0.3 flame doped with 0.85 wppm of sodium. The change of inductance was found to define the known corrosion behavior and to suggest its use as a tool with predictive capabilities. Sufficient sensitivity exists to detect oxidation of this alloy at 900 C.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83560 , E-1937 , NAS 1.15:83560
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  • 82
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    Study of proton and neutron activation of metal samples in low Earth orbit (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The analysis of the gamma-ray spectra taken from samples flown in Spacelab 1; the search for and review of neutron and proton activation cross-sections needed to analyze the results of the Long Duration Exposure Facility (LDEF) activation measurements; additional calculations of neutron induced activation for the LDEF samples; the data analysis plan for the LDEF and Spacelab 2 samples; the measurement of relevant cross-sections with activation of samples of V, Co, In, and Ta at the Indiana University Cyclotron Facility; and the preparation of an extended gamma-ray calibration source through the development of a proper technique to accurately deposit equal quantities of radioactive material onto a large number of point on the source are discussed.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-171183 , NAS 1.26:171183
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  • 83
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    Morphological changes of gamma prime precipitates in nickel-base superalloy single crystals (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Changes in the morphology of the gamma prime precipitate were examined during tensile creep at temperatures between 927 and 1038 C in 001-oriented single crystals of a Ni-Al-Mo-Ta superalloy. In this alloy, which has a large negative misfit of -0.80%, the gamma prime particles link together during creep to form platelets, or rafts, which are aligned with their broad faces perpendicular to the applied tensile axis. The dimensions of the gamma and gamma prime phases were measured as directional coarsening developed in an attempt to trace the changing morphology under various stress levels. In addition, the effects of initial microstructure, as well as slight compositional variations, were related to raft development and creep properties. The results showed that directional coarsening of gamma prime began during primary creep, and under certain conditions, continued to develop after the onset of steady-state creep. The length of the rafts increased linearly with time up to a plateau region. The thickness of the rafts, however, remained equal to the initial gamma prime size at least up through the onset of tertiary creep; this is a clear indication of the stability of the finely-spaced gamma-gamma prime lamellar structure. It was found that the single crystals with the finest gamma prime size exhibited the longest creep lives, because the resultant rafted structure had a larger number of gamma-gamma prime interfaces per unit volume of material.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83698 , E-2156 , NAS 1.15:83698
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  • 84
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    Studies on the hot corrosion of a nickel-base superalloy, Udimet 700 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The hot corrosion of a nickel-base superalloy, Udimet 700, was studied in the temperature range of 884 to 965 C and with different amounts of Na2SO4. Two different modes of degradation were identified: (1) formation of Na2MoO4 - MoO3 melt and fluxing by this melt, and (2) formation of large interconnected sulfides. The dissolution of Cr2O3, TiO2 in the Na2SO4 melt does not play a significant role in the overall corrosion process. The conditions for the formation of massive interconnected sulfides were identified and a mechanism of degradation due to sulfide formation is described. The formation of Ns2MoO4 - MoO3 melt requires an induction period and various physiochemical processes during the induction period were identified. The factors affecting the length of the induction period were also examined. The melt penetration through the oxide appears to be the prime mode of degradation whether the degradation is due to the formation of sulfides or the formation of the Na2MoO4 - MoO3 melt.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-86882 , E-2314 , NAS 1.15:86882
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  • 85
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    The effect of tantalum and carbon on the structure/properties of a single crystal nickel-base superalloy (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The microstructure, phase chemistry, and creep and hot tensile properties were studied as a function of tantalum and carbon levels in Mar-M247 type single crystal alloys. Microstructural studies showed that several types of carbides (MC, M23C6 and M5C) are present in the normal carbon (0.10 wt % C) alloys after heat treatment. In general, the composition of the MC carbides changes from titanium rich to tantalum rich as the tantalum level in the alloy increases. Small M23C6 carbides are present in all alloys. Tungsten rich M6C carbides are also observed in the alloy containing no tantalum. No carbides are present in the low carbon (0.01 wt % C) alloy series. The morphology of gamma prime is observed to be sensitive to heat treatment and tantalum level in the alloy. Cuboidal gamma prime is present in all the as cast structures. After heat treatment, the gamma prime precipitates tend to have a more spheroidal like morphology, and this tendency increases as the tantalum level decreases. On prolonged aging, the gamma prime reverts back to a cuboidal morphology or under stress at high temperatures, forms a rafted structure. The weight fraction and lattice parameter of the spheroidal gamma prime increases with increasing tantalum content. Changes in the phase chemistry of the gamma prime matrix and gamma prime have also been analyzed using phase extraction techniques. The partitioning ratio decreases for tungsten and aluminum and increases for tantalum as the tantalum content increases for both alloy series; no significant changes occur in the partitioning ratios of the other alloying elements. A reduction in secondary creep rate and an increase in rupture time result from increasing the tantalum content and decreasing the carbon level.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174779 , NAS 1.26:174779
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  • 86
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    An electrochemical study of hydrogen uptake and elimination by bare and gold-plated waspaloy (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Two electrochemical methods for the determination of hydrogen concentrations in metals are discussed and evaluated. The take-up of hydrogen at a pressure of 5000 psi by Waspaloy metal was determined experimentally at 24 C. It was found that the metal becomes saturated with hydrogen after an exposure time of about 1 hr. For samples charged with hydrogen at high pressure, most of the hydrogen is contained in the interstitial solid solution of the metal. For electrolytically charged samples, most of the hydrogen is contained as surface and subsurface hydrides. Hydrogen elimination rates were determined for these two cases, with the rate for electrolytically charged samples being greater by over a factor of two. Theoretical effects of high temperature and pressure on hydrogen take-up and elimination by bare and gold plated Waspaloy metal was considered. The breakthrough point for hydrogen at 5000 psi, determined experimentally, lies between a gold thickness of 0.0127 mm (0.0005 in.) and 0.0254 mm (0.001 in.) at 24 C. Electropolishing was found to greatly reduce the uptake of hydrogen at high pressure by Waspaloy metal at 24 C. Possible implications of the results obtained, as they apply to the turbine disk of the space shuttle main engine, are discussed.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-86479 , NAS 1.15:86479
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  • 87
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    Effect of humidity on fretting wear of several pure metals (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Fretting wear experiments with several pure metals were conducted in air at various relative humidity levels. The materials used were iron, aluminum, copper, silver, chromium, titanium, and nickel. Each pure metal had a maximum fretting wear volume at a specific humidity level RH sub max that was not dependent on mechanical factors such as contact load, fretting amplitude, and frequency in the ranges studied. The weight loss due to fretting wear at RH sub max for each pure metal decreased with increasing heat of oxygen adsorption on the metal, indicating that adhesive wear dominated at RH sub max.
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2403 , E-2184 , NAS 1.60:2403
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  • 88
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    High-pressure hydrogen testing of single crystal superalloys for advanced rocket engine turbopump turbine blades (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A screening program to determine the effects of high pressure hydrogen on selected candidate materials for advanced single crystal turbine blade applications is examined. The alloys chosen for the investigation are CM SX-2, CM SX-4C, Rene N-4, and PWA1480. Testing is carried out in hydrogen and helium at 34 MPa and room temperature, with both notched and unnotched single crystal specimens. Results show a significant variation in susceptibility to Hydrogen Environment Embrittlement (HEE) among the four alloys and a marked difference in fracture topography between hydrogen and helium environment specimens.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-86464 , NAS 1.15:86464
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  • 89
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    Crack tip field and fatigue crack growth in general yielding and low cycle fatigue (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Fatigue life consists of crack nucleation and crack propagation periods. Fatigue crack nucleation period is shorter relative to the propagation period at higher stresses. Crack nucleation period of low cycle fatigue might even be shortened by material and fabrication defects and by environmental attack. In these cases, fatigue life is largely crack propagation period. The characteristic crack tip field was studied by the finite element method, and the crack tip field is related to the far field parameters: the deformation work density, and the product of applied stress and applied strain. The cyclic carck growth rates in specimens in general yielding as measured by Solomon are analyzed in terms of J-integral. A generalized crack behavior in terms of delta is developed. The relations between J and the far field parameters and the relation for the general cyclic crack growth behavior are used to analyze fatigue lives of specimens under general-yielding cyclic-load. Fatigue life is related to the applied stress and strain ranges, the deformation work density, crack nucleus size, fracture toughness, fatigue crack growth threshold, Young's modulus, and the cyclic yield stress and strain. The fatigue lives of two aluminum alloys correlate well with the deformation work density as depicted by the derived theory. The general relation is reduced to Coffin-Manson low cycle fatigue law in the high strain region.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174686 , NAS 1.26:174686
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  • 90
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    Influence of soft inclusions on the strength of wrought materials (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The three dimensional soft particles (such as sulfides, silicates and voids) present in most materials are modelled by circular voids in sheet metal. Relationships are sought between the shape and orientation of a hole after rolling and testing in tension. Then, the effect of hole shape and size on mechanical properties is considered experimentally. The presence of voids has a negligible influence on the ultimate tensile stress of ductile materials based on the unperforated area because plastic flow neutralizes the stress intensification present in the elastic region. However, the shape and orientation of the defects are found to play an important role relative to strain at fracture. In certain engineering applications the strain at fracture is more important than the stress at fracture and in this sense the presence of voids are considered to influence the strength of a ductile material.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-173610 , NAS 1.26:173610
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  • 91
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    Effects of surface chemistry on hot corrosion life (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Baseline burner rig hot corrosion with Udimet 700, Rene' 80; uncoated and with RT21, Codep, or NiCoCrAlY coatings were tested. Test conditions are: 900C, hourly thermal cycling, 0.5 ppm sodium as NaCl in the gas stream, velocity 0.3 Mach. The uncoated alloys exhibited substantial typical sulfidation in the range of 140 to 170 hours. The aluminide coatings show initial visual evidence of hot corrosion at about 400 hours, however, there is no such visual evidence for the NiCoCrAlY coatings. The turbine components show sulfidation. The extent of this distress appeared to be inversely related to the average length of mission which may, reflect greater percentage of operating time near ground level or greater percentage of operation time at takeoff conditions (higher temperatures). In some cases, however, the location of maximum distress did not exhibit the structural features of hot corrosion.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174683 , NAS 1.26:174683 , R84AEB422 , AR-1
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  • 92
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    Separation processes during binary monotectic alloy production (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observation of microgravity solidification processes indicates that outside of sedimentation, at least two other important effects can separate the phases: critical-point wetting and spreading; and thermal migration of second-phase droplets due to interfacial tension gradients. It is difficult to study these surface tension effects while in a unit gravity field. In order to investigate the processes occurring over a temperature range, i.e., between a consolute point and the monotectic temperature, it is necessary to use a low-gravity environment. The MSFC drop tube (and tower), the ballistic trajectory KC-135 airplane, and the Space Shuttle are ideal facilities to aid formation and testing of hypotheses. Much of the early work in this area focuses on transparent materials so that process dynamics may be studied by optical techniques such as photography for viewing macro-processes; holography for studying diffusional growth; spinodal decomposition and coalescence; ellipsometry for surface wetting and spreading effects; and interferometry and spectroscopy for small-scale spatial resolution of concentration profiles.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-82579 , NAS 1.15:82579
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  • 93
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    Microstructures Associated with Wear (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: High strain associated with metal wear is discussed and macroscopic and fine microscopic aspects are included. Mechanisms for the production of debris which include extrusion of microfurrows, adhesive transfer, and fragmentation are outlined. The structure of near surface deformation zones, a thin transfer layer, is examined. The similarity among the size of fine wear debris particles, the structure of the transfer layer, and large wear flakes is shown. Differences in microstructure associated with dry wear and lubricated wear are pointed out. Some parallels and differences for classic high strain deformation and wear microstructures are discussed.
    Keywords: METALLIC MATERIALS
    Type: NASA Lewis Research Center Tribology in the 80's. Vol. 1; p 219-235
    Format: text
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  • 94
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    Response of Inconel 617 superalloy to combined ground-based and STS reentry exposure (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Inconel 617 is a nickel-based superalloy which is being considered for heat-shield applications because of its high-temperature strength, good oxidation resistance and high emittance of oxidized surfaces. While the effects of simulated reentry conditions on emittance and oxidation of Inconel 617 have been studied, the combined effects of the ground-based environment with sea salt exposure and the reentry environment have not been evaluated. Experimental results are presented to show the effects of environmental simulation including ground-based and reentry exposure on the emittance and oxidation of Inconel 617. Specimens were exposed to simulated reentry at a surface temperature of 2000 F in the Langley Research Center Hypersonic Materials Environmental Test System (HYMETS) Facility with and without alternate exposures to an atmospheric seashore environment or a laboratory sea salt environment. This paper presents emittance, mass loss, oxide chemistry, and alloy composition data for the specimens.
    Keywords: METALLIC MATERIALS
    Type: AIAA PAPER 84-1768
    Format: text
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  • 95
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    Creep-rupture behavior of six candidate Stirling engine superalloys tested in air (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The creep-rupture behavior of six candidate Stirling engine iron-base superalloys was determined in air. The alloys included four wrought alloys (A-286, Alloy 800H, N-155, and 19-9DL) and two cast alloys (CRM-6D and XF-818). The specimens were tested to rupture for times up to 3000 h at 650 to 925 C. Rupture life, t(r) minimum creep rate, and time to 1-percent creep strain t(0.01) were statistically analyzed as a function of stress and temperature. Estimated stress levels at different temperatures to obtain 3500 h t(r) and t(0.01) lives were determined. These data will be compared with similar data being obtained under 15 MPa hydrogen.
    Keywords: METALLIC MATERIALS
    Type: ASME, Transactions, Journal of Engineering Materials and Technology (ISSN 0094-4289); 106; 50-58
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  • 96
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    Evaluation of candidate Stirling engine heater tube alloys after 3500 hours exposure to high pressure doped hydrogen or helium (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The heater head tubes of current prototype automotive Stirling engines are fabricated from alloy N-155, an alloy which contains 20 percent cobalt. Because the United States imports over 90 percent of the cobalt used in this country and resource supplies could not meet the demand imposed by automotive applications of cobalt in the heater head (tubes plus cylinders and regenerator housings), it is imperative that substitute alloys free of cobalt be identified. The research described herein focused on the heater head tubes. Sixteen alloys (15 potential substitutes plus the 20 percent Co N-155 alloy) were evaluated in the form of thin wall tubing in the NASA Lewis Research Center Stirling simulator materials diesel fuel fired test rigs. Tubes filled with either hydrogen doped with 1 percent CO2 or with helium at a gas pressure of 15 MPa and a temperature of 820 C were cyclic endurance tested for times up to 3500 hr. Results showed that two iron-nickel base superalloys, CG-27 and Pyromet 901 survived the 3500 hr endurance test. The remaining alloys failed by creep-rupture at times less than 3000 hr, however, several other alloys had superior lives to N-155. Results further showed that doping the hydrogen working fluid with 1 vol % CO2 is an effective means of reducing hydrogen permeability through all the alloy tubes investigated.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83782 , E-2276 , DOE/NASA/51040-56 , NAS 1.15:83782
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  • 97
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    Tensile Fracture of Ductile Materials (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: For brittle materials, circular voids play an important role relative to fracture, intensifing both tensile and compressive stresses. A maximum intensified tensile stress failure criterion applies quite well to brittle materials. An attempt was made to explore the possibility of extending the approach to the tensile fracture of ductile materials. The three dimensional voids that exist in reality are modelled by circular holes in sheet metal. Mathematical relationships are sought between the shape and size of the hole, after the material is plastically deformed, and the amount of deformation induced. Then, the effect of hole shape, size and orientation on the mechanical properties is considered experimentally. The presence of the voids does not affect the ultimate tensile strength of the ductile materials because plastic flow wipes out the stress intensification caused by them. However, the shape and orientation of the defect is found to play an important role in affecting the strain at fracture.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-173607 , NAS 1.26:173607
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  • 98
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    Friction and wear of nickel in sulfuric acid (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experiments were conducted with elemental nickel sliding on aluminum oxide in aerated sulfuric acid in concentrations ranging from very dilute (10 -4 N, i.e., 5 ppm) to very concentrated (96 percent) acid. Load and reciprocating sliding speeds were kept constant. With the most dilute concentration (10 -4 N) no observable corrosion occurred in or outside the wear area. This was used as the base condition to determine the high contribution of corrosion to total wear loss at acid concentrations between 0.5 percent (0.1 N) and 75 percent. Corrosion reached a maximum rate of 100 millimeters per year at 30 percent acid. At the same time, general corrosion outside the wear area was very low, in agreement with published information. It is clear that friction and wear greatly accelerated corrosion in the wear area. At dilute concentrations of 0.001 and 0.01 N, corrosion in the wear area was low, and general corrosion outside was also low, but local outside regions in the direction of the wear motion experienced some enhanced corrosion, apparently due to fluid motion of the acid.
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2290 , E-1817 , NAS 1.60:2290
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  • 99
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    Influence of cobalt, tantaum and tungsten on the high temperature mechanical properties of single crystal nickel-base superalloys (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: For alloys with the baseline refractory metal level of 3 percent Ta and 10 percent W, decreases in Co level from 10 to 0 percent resulted in increased tensile strength and creep resistance. Substitution of W for Ta resulted in decreased creep life at high stresses but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta plus W totals, strength was independent of Co level. The increases in tensile strength with increases in refractory metal content were related to the increases in gamma volume fraction and solid solution hardening. Increases in strength as Co level decreased were considered to be the result of coherency strain hardening from the increased lattice mismatch. Dislocation shear through the gamma-gamma interface is considered to be the rate limiting step in the deformation process.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83479 , E-1796 , NAS 1.15:83479
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  • 100
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    Preliminary study of thermomechanical fatigue of polycrystalline MAR-M 200 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Thermomechanical fatigue (TMF) experiments were conducted on polycrystalline MAR-M 200 over a cyclic temperature range of 500 to 1000 C. Inelastic strain ranges of 0.03 to 0.2 percent were imposed on the specimens. The TMF lives were found to be significantly shorter than isothermal low-cycle-fatigue (LCF) life at the maximum cycle temperature, and in-phase cycling was more damaging than out-of-phase cycling. Extensive crack tip oxidation appeared to play a role in promoting the severity of in-phase cycling. Carbide particle - matrix interface cracking was also observed after in-phase TMF cycling. The applicability of various life prediction models to the TMF results obtained was assessed. It was concluded that current life prediction models based on isothermal data as input must be modified to be applicable to the TMF results.
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2280 , E-1795 , NAS 1.60:2280 , AVSCOM-TR-83-C-6
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