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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1940

Creep Strength of Stabilized Wrought-aluminum Alloys

Rohn-type equipment has been mounted on rubber blocks, for the purpose of damping the vibrations of the ground and of rendering the plastic yielding of the test bars less subject to outside interferences. New equipment also included three shockproof creep-testing machines with the Martens mirror instruments for recording the strain curve of the fatigue-tested specimens.

Muller, W↗
NASA NTRS1993

Effect of Long-Term 1093 K Exposure to Air or Vacuum on the Structure of Several Wrought Superalloys

Long-term 1093 K heat treatments of three commercial superalloy sheet materials were undertaken in air -IAI and vacuum. With either exposure, significant precipitation of second phases occurred in the Co-base Haynes(R) Alloy 188 (HA 188) and the Ni-base Haynes(R) Alloy 230 (HA 230); however, much less precipitation was found in the exposed Ni-base alloy Inconel(R) 617 (IN 617). Although some grain growth occurred in HA 198, no changes in the grain size of either HA 230 or IN 617 were observed after 22,500 h at temperature. Oxidation during air heat treatments led to weight gain due to the formation of chromia + spinel scales and surface-connected grain boundary pits/oxides in all three superalloys. Both the weight gain and depth of intergranular attack were dependent on the square root of time, which is indicative of diffusion-controlled phenomena. Because many alloy samples had neighbors in close proximity, most vacuum heat treated specimens did not suffer significant loss of volatile elements. However, some exposed samples were subjected to unrestricted vacuum heat treatments, allowing estimates of volatilization to be made. Based on the data for HA 188, the weight loss during 1093 K vacuum exposure was diffusion controlled once the inhibiting effects of surface films on the as-received alloys were broken down.

J.D. Whittenberger↗
NASA NTRSDate not supplied

Analysis of Additively Manufactured Inconel 718 Combustion Behavior in Promoted Oxygen Environments

Promoted combustion testing is a vital tool for engineers to establish the combustion and flammability characteristics of materials (metallic or otherwise) in oxygen enriched environments. Historically, much of the established data for metallic promoted combustion has been with regards to cast and wrought forms. However, with the emergence of additive manufacturing as a preferred method of fabrication, the need exists to evaluate how metals in that form behave. This paper will serve as a review of the work that has been done and an analysis of the nickel-based superalloy Inconel 718, a material popular for aerospace applications such as liquid fueled rocket components and turbine engines. Promoted combustion testing (per the ASTM G124 standard) was conducted on samples of both wrought and selective laser melted fabrication, to provide comparison of flammability response between materials produced by each manufacturing method. Additionally, post-build treatments were applied to test samples to identify any effects on performance provided by hot isostatic pressing, oxygen-getting wrap during HIP, stress relieving, and solutionizing/aging heat treatments. This study will utilize optical and scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, and metallography to identify the differences in behavior of additively manufactured and wrought Inconel 718.

Additively Manufactured↗
NASA NTRS2026

Fatigue Life of Flow-Formed Aluminum 2195 and 6061 Alloys

The successful design and fabrication of metallic cryotanks for commercial aviation applications require lightweight, durable materials capable of withstanding high pressures and cryogenic temperatures through tens of thousands of thermomechanical refueling cycles. Flow forming is an advanced manufacturing technique that offers high-rate production and scalability for fabricating integrally stiffened cylinders suitable for cryotank applications. This work establishes the durability of flow-formed aluminum alloys by characterizing their fatigue life performance under conditions that mimic cryotank refueling cycles. Residual stresses in flow-formed aluminum-lithium (Al-Li) 2195-T6 cylinders were assessed using the contour method and found to be minimal. Fatigue life testing was conducted on flow-formed Al-Li 2195-T6 at room temperature and cryogenic temperatures (-321°F [-196°C]), with wrought Al-Li 2195-T6 serving as a baseline for comparison. Results showed that flow-formed materials exhibited fatigue performance comparable to or better than wrought materials, with no statistically significant differences observed between different specimen orientations relative to processing directions. Fractography revealed reduced delaminations in the flow-formed Al-Li 2195 samples as compared to wrought, indicating potential improvement to the microstructure that could result in improved service properties. Texture analysis using electron backscattered diffraction (EBSD) indicated recrystallization during heat treatment, potentially contributing to reduced delamination susceptibility. These findings demonstrating flow-formed material durability coupled with the high manufacturing efficiency of flow forming, makes flow forming an attractive process to produce aircraft cryotanks.

EBF3↗
NASA NTRS1972

Properties of materials in high pressure hydrogen at room and elevated temperatures

Experimental efforts in this program for this period. Mechanical property tests of wrought and cast nickel-base alloys and one wrought cobalt-base alloy were conducted in 34.5 MN/sq m (5000-psig) helium and hydrogen or hydrogen mixtures. Comparison of test results was made to determine degradation of properties due to the hydrogen environments. All testing was conducted on solid specimens exposed to external gaseous pressure. Specific mechanical properties determined and the testing methods used are summarized.

Harris, J. A., Jr.↗
NASA NTRS1970

Properties of Hot Pressed Titanium Alloy Powders for Cryogenic Applications.

Evaluation of strength and toughness of hot-pressed titanium alloy powders at room and at cryogenic temperatures. The purpose was to determine how the mechanical properties of solid bodies formed from powder would compare with wrought specimens of the same size and with the same chemical analysis. It was found that of five titanium powder-making processes investigated, only the Rotating Electrode Process (REP) was capable of producing ELI-grade titanium alloy powder. Blocks hot-pressed from spherical REP powders had tensile properties equivalent to or better than those obtained from wrought bar.

Friedman, G. I.↗
NASA NTRS1973

Development of ductile high-strength chromium alloys, phase 2

Strength and ductility were evaluated for chromium alloys dispersion hardened with the putative TaC, TaB, CbC, and CbB compounds. TaC and TaB proved to be the most potent strengtheners, but when combined, their effect far outweighed that produced individually. Tests at 1422 K (2100 F) on an alloy containing these two compounds at the combined level of 0.5 m/o revealed a 495 MN/sq m (70 ksi) tensile strength for wrought material, and a 100 hour rupture strength of 208 MN/sq m (30 ksi) when solution annealed and aged to maximize creep resistance. These levels of high temperature strength greatly exceed that reported for any other chromium-base alloy. The ductile-to-brittle transition temperature (DBTT) of the two phase strengthened alloy occurred at approximately 588 K (600 F) when heat treated to optimize creep strength and was not improved by fabrication to produce a wrought and recovered microstructure. The lowest DBTT measured on any of the alloys investigated was 422 K (300 F). Strengthening phases actually formed in Cr-Ta-B and Cr-Cb-B compositions are probable M2CrB2 (M=Ta or Cb) compounds of tetragonal crystal structure. The likely habit relationship between these compounds and chromium is postulated. Cube habit coherency was identified for TaC precipitation in chromium by electron microscopy. In another study, the maximum solubility of carbon in chromium was indicated to lie between 3/4 and 1 a/o and that of boron to be 1/2 a/o.

Filippi, A. M.↗
NASA NTRS1978

The effect of microstructure on hydrogen embrittlement of the nickel-base superalloy, Udimet 700

Material from a single heat of cast and wrought Udimet 700 was processed and/or heat treated to produce five material conditions with identical chemical compositions but with distinct microstructural variations, and then evaluated for susceptibility to hydrogen embrittlement. Two prealloyed powder conditions exhibited significantly improved resistance to hydrogen embrittlement, as compared to wrought material. No degradation in notch or smooth tensile strengths occurred, and average ductilities of 25 percent reduction of area were determined for 2 hydrogen evaluation procedures. For the most severe hydrogenation procedure, ductility levels were reduced to 15 percent. These improvements were attributed to cleaner grain boundaries and decreases grain size.

Gray, H. R.↗
NASA NTRS1978

The effect of microstructure on hydrogen embrittlement of the nickel base superalloy, Udimet 700

Material from a single heat of cast and wrought Udimet 700 was processed and/or heat treated to produce five material conditions with identical chemical compositions but with distinct microstructural variations, and then evaluated for susceptibility to hydrogen embrittlement. Two prealloyed powder conditions exhibited significantly improved resistance to hydrogen embrittlement, as compared to wrought material. No degradation in notch or smooth tensile strengths occurred, and average ductilities of 25 percent reduction of area were determined for 2 hydrogen evaluation procedures. For the most severe hydrogenation procedure, ductility levels were reduced to 15 percent. These improvements were attributed to cleaner grain boundaries and decreased grain size.

Gray, H. R.↗
NASA NTRS1979

Development of sputtered techniques for thrust chambers

The 0.152 cm thick sputtered and copper deposits were electron beam welded to wrought copper. Tensile specimens were machined from the weld assemblies and tested at room temperature. Tensile strength approached the strength of wrought material. Elongations up to 25% were measured. Sputtered aluminum was used to fill 0.157 cm wide by 0.127 cm deep grooves in thrust chamber spool piece liners. The liners were closed out by sputtering copper from post and hollow cathodes.

Mullaly, J. R.↗
NASA NTRS1978

Fracture resistance of Ti-5Al-2.5Sn extra-low interstitial castings

Fracture toughness and cyclic crack propagation data for Ti-5Al-2.5Sn extra-low interstitial (ELI) castings, 0.51 and 2.54 cm (0.20 and 1.00 in.) thick, at 394, 294, 77, and 20 K (250, 70, -320, and -423 F), are presented. Both surface flaw and compact tension geometries were tested. Comparison is made with other titanium alloys in both wrought and cast forms. Crack propagation resistance is comparable to wrought Ti-5Al-2.5Sn ELI, even with the extremely coarse as-cast grain size encountered.

Fiftal, C. F.↗