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  • 1
    Publication Date: 2013-08-31
    Description: The literature, applicable theory and finally an experimental program were used to identify new candidate alloy systems for use as the electrical resistance elements in static strain gages up to 1250K. The program goals were 50 hours of use in the environment of a test stand gas turbine engine with measurement accuracies equal to or better than 10 percent of full scale for strains up to + or - 2000 microstrain. As part of this effort, a computerized electrical resistance measurement system was constructed for use at temperatures between 300K and 1250K and heating and cooling rates of 250K/min and 10K/min. The two best alloys were an iron-chromium-aluminum alloy and a palladium base alloy. Although significant progress was made, it was concluded that a considerable additional effort would be needed to fully optimize and evaluate these candidate systems.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NAS 1.26:174833 , R85-915952-13 , NASA-CR-174833
    Format: application/pdf
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  • 2
    Publication Date: 2013-08-31
    Description: A program was performed to address the mechanical and environmental needs of Stirling engine heater head and regenerator housing components, while reducing the dependence on strategic materials. An alloy was developed which contained no strategic elemental additions per se. The base is iron with additions of manganese, molybdenum, carbon, silicon, niobium, and ferro-chromium. Such an alloy should be producible on a large scale at very low cost. The resulting alloy, designated as NASAUT 4G-Al, contained 15 Mn, 15 Cr, 2 Mo, 1.5 C, 1.0 Si, 1.0 Nb (in weight percent) with a balance of Fe. This alloy was optimized for chemistry, based upon tensile strength, creep-rupture strength, fracture behavior, and fatigue resistance up to 800 C. Alloys were also tested for environmental compatibility. The microstructure and mechanic properties (including hardness) were assessed in the as-cast condition and following several heat treatments, including one designed to simulate a required braze cycle. The alloy was fabricated and characterized in the form of both equiaxed and columnar-grained castings. The columnar grains were produced by directional solidification, and the properties were characterized in both the longitudinal and transverse orientations. The NASAUT 4G-Al alloy was found to be good in cyclic-oxidation resistance and excellent in both hydrogen and hot-corrosion resistance, especially in comparison to the baseline XF-818 alloy. The mechanical properties of yield strength, stress-rupture life, high-cycle-fatigue resistance, and low-cycle-fatigue resistance were good to excellent in comparison to the current alloy for this application, HS-31 (X-40), with precise results depending in a complex manner on grain orientation and temperature. If required, the ductility could be improved by lowering the carbon content.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-185174 , DOE/NASA/0282-1 , R89-917447-32 , NAS 1.26:185174
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  • 3
    Publication Date: 2016-06-07
    Description: Low cost cast ferrous base alloys that can be used for cylinder and regenerator housing components of the Stirling engine were investigated. The alloys must meet the requirements of high strength and thermal fatigue resistance to approximately 1500 F, compatibility and low permeability with hydrogen, good elevated temperature oxidation/corrosion resistance, and contain a minimum of strategic elements. The phase constituents of over twenty alloy iterations were examined by X-ray diffraction. These alloy candidates were further screened for their tensile and stress rupture strength and surface stability in air at 1450 and 1600 F, respectively. Two alloys, NASAUT 1G (Fe-10Mn-20Cr-1.5C-1.0Si) and NASAUT 4G (Fe-15Mn-12Cr-3Mo-1.5C-1.0Si-1.0Nb), were chosen for more extensive elevated temperature testing. These alloys were found to exhibit nearly equivalent elevated temperature creep strength and oxidation resistance. Silicon present in these alloys at the 1 w/o level permitted the achievement of oxide scale adherence to 1600 F without loss of strength (or ductility) as was noted for equivalent additions of aluminum.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center COSAM (Conserv. of Strategic Aerospace Mater.) Program Overview; p 209-214
    Format: text
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  • 4
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    In:  Other Sources
    Publication Date: 2016-06-07
    Description: Iron base alloys containing aluminum and chromium together with smaller amounts of yttrium and silicon are of interest for high temperature applications. Strengthening an inherently weak but oxidation resistant solid solution matrix with aligned in situ chromium carbides represents an attractive approach to achieving both surface stability and creep resistance at elevated temperatures. Aligned microstructures were produced in alloys of approximately 30 wt % (Cr + Mn), about 3 wt % C and the balance Fe consisting of a gamma matrix and the hexagonal carbide (Cr, Mn, Fe)7C3. The tensile and stress rupture strength to 2000 F of aligned Fe-20 w/t % Cr-10 wt % Mn-3.2 wt % C measured parallel to the carbide reinforcement exceeded those of the strongest iron-nickel superalloys, e.g., CRM-6D developed by Chrysler for automotive turbine application. The cyclic oxidation and sulfidation response of these alloys at elevated temperatures can be markedly improved by aluminum additions.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center COSAM (Conserv. of Strategic Aerospace Mater.) Program Overview; p 203-208
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  • 5
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Duplex microstructures of iron-base superalloys, consisting of an austenitic matrix and a M7C3 carbide, can be produced within the Fe-Mn-Cr-Mo-Al (Si)-C systems. The stability regions of the carbides were inspected by means of isothermal sections of alloys in the quinary combination Fe-Mn-Cr-Mo-C for 70 at% metal and 30 at % carbon. For 35 at % iron the competing carbides are found to be M2C, M3C and the molybdenum cementite (MoFe2C) in the arc-melted state, with M23C6 in the annealed state. In the quaternary system, Fe-Mn-Mo-C, a M2C carbide forms, presumaby derived from a solid solution carbide, (Mn, Mo)2C. In extracted carbides of cast alloys containing Fe-Mn-Cr-Mo-Al (Si)-C a considerable amount of the π-phase carbide occurs.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In the course of studies on the iron-rich multicomponent system Fe-Mn-Cr-Mo-Nb-Al-Si-C, work was concentrated on pertinent quinary and six-component combinations namely Fe-Mn-Al-Si-C, Fe-Cr-Al-Si-C and Fe-Mn-Cr-Al-Si-C which had been elaborated at 65, 72, and 80wt% Fe. From these systems the following conclusions are obvious. Manganese acts as a strong stabilizer for the cementite carbide. Chromium and silicon, when present together prefer to occur as separate phases. However, a small portion is found as intermetallics such as CrSi2 or (Fe, Mn)5Si3. Chromium seems to stabilize the iron aluminide Fe2Al5 which forms in a considerable amount within an alloy of nominal composition Fe(65)Mn(15)Cr(12) Al(5)Si(2)C(1) (per cent by weight). Although the Mn3AlC carbide is, like Fe3AlC, a perovskite carbide, manganese does not appear to favour the formation of the perovskite carbide. Because of the relatively low sintering temperature (700° C), for a large portion of the samples equilibria conditions are not always reached. Furthermore, due to this temperature, iron is in the ferritic state.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 2011-08-18
    Description: The optimization of high carbon iron-base superalloy properties with duplex microstructure gamma + M7C3 carbide requires analysis in the context of a seven-component system. Data are first provided here for the Fe-Mn-Cr-Mo-C quinary system, at 30 at. pct carbon. A characterization of competing carbides, according to a pseudoternary phase diagram at 35 wt pct iron, is made from isothermal sections. It is noted that while M7C3 and M3C carbides' occurrences are respectively favored at the Cr and Mn corners, the M2C carbide and molybdenum cementite are predominant with increasing amounts of Mo. Lattice parameters are reported for the various carbides.
    Keywords: METALLIC MATERIALS
    Type: Journal of Materials Science (ISSN 0022-2461); 19; 965-973
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  • 8
    Publication Date: 2013-08-31
    Description: By means of a screening and solidification optimization study of certain alloys located on the gamma-sigma liquidus surface within the Ni-Cb-Cr-Al system, alloys with high temperature properties superior to those of all known superalloys were defined. One alloy, Ni - 19.7w/o Cb - 6.0w/o Cr - 2.5w/o Al, directionally solidified at 3 cm/hr met or exceeded each program goal. A second alloy, Ni-21.75 w/o Cb-2.55 w/o Al, although deficient in its inherent oxidation resistance, met the other program goals and combined a remarkable insensitivity of composite microstructure to solidification parameters with excellent low temperature toughness. This investigation demonstrated that useful properties for gas turbine airfoil application have been achieved by reinforcing a strong and tough gamma solid solution matrix containing precipitated gamma prime by a lamellar intermetallic compound Ni3 Cb having greater strength at elevated temperature.
    Keywords: MATERIALS, METALLIC
    Type: M911213-5 , NASA-CR-2278
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  • 9
    Publication Date: 2013-08-31
    Description: By means of a compositional and heat treatment optimization program based on the quaternary gamma/gamma prime-delta, a tantalum modified gamma/gamma prime-delta alloy with improved shear and creep strength combined with better cyclic oxidation resistance was identified. Quinary additions, quaternary adjustments, and heat treatment were investigated. The tantalum modified gamma/gamma prime-delta alloy possessed a slightly higher liquidus temperature and exhibited rupture strength exceeding NASA VIA by approximately three and one-half Larson-Miller parameters (C = 20) above 1000 C. Although improvements in longitudinal mechanical properties were achieved, the shear and transverse strength property goals of the program were not met and present a continuing challenge to the alloy metallurgist.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-134678 , R911698-13
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  • 10
    Publication Date: 2011-04-14
    Description: Alloy has high temperature properties exceeding strength of all known superalloys. It exhibits inherent resistance to oxidation and high temperature hot corrosion.
    Keywords: MATERIALS
    Type: LEW-12562
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