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  • METALLIC MATERIALS  (7)
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  • 1
    facet.materialart.
    Unknown
    Identification of a cast iron alloy containing nonstrategic elements (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    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 , NAS 1.26:185174 , R89-917447-32
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    Elevated temperature properties of aligned ferrous eutectics (1982)
    In:  Other Sources
    Details
    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
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Unknown
    Development of cast ferrous alloys for Stirling engine application (1982)
    In:  Other Sources
    Details
    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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    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unknown
    Carbides in iron-rich Fe-Mn-Cr-Mo-Al-Si-C systems (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    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
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Quaternary and quinary modifications of eutectic superalloys strengthened by delta Ni3Cb lamellae and gamma prime Ni3Al precipitates (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    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
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Unknown
    Iron-base superalloys - A phase analysis of the multicomponent system (Fe-Mn-Cr-Mo-Nb-Al-Si-C) (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: 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 80 wt pct Fe. Manganese acts as a strong stabilizer for the cementite carbide. 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) (percent by weight). Although the Mn3AlC carbide is, like Fe3AlC, a perovskite carbide, manganese does not appear to favor the formation of the perovskite carbide. Because of the relatively low sintering temperature (700 C), for al large portion of the samples equilibria conditions are not always reached.
    Keywords: METALLIC MATERIALS
    Type: Journal of Materials Science (ISSN 0022-2461); 23; 3113-311
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    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    High-temperature oxidation/corrosion of iron-based superalloys (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The oxidation and sulfidation of several novel iron-base superalloys were evaluated in high-temperature cyclic tests. The experimental austenitic alloys examined were modifications of NASAUT-4GA which were developed for Stirling-engine application. The weight gains and resulting surface scales were measured and analyzed. Mixed oxide scales were found to form on all specimens exposed above 871 C. The build-up of these scales led to a depletion of Mn and Cr in a zone adjacent to the oxides. In addition, the initial oxidation of the Fe-rich alloy was inhibited by a thin but tenacious Si layer which formed at the interface between oxides and the parent layer. Sulfidation tests using Na2SO4 coatings resulted in the formation of a protective spinel and alpha-Fe2O3 phases. Preferential attack of the carbide phase by hydrogen was not observed after 350 h at 871 C.
    Keywords: METALLIC MATERIALS
    Type: Alternate alloying for environmental resistance; Mar 02, 1986 - Mar 06, 1986; New Orleans, LA; United States
    Format: text
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    NASA TECHNICAL REPORTS
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