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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Effect of W and WC on the oxidation resistance of yttria-doped silicon nitride

The effect of W and WC contamination on the oxidation and cracking in air of sintered Si3N4 - 8 w/o Y2O3 ceramics at 500, 750, and 1350 C is examined. A mixture of Si3N4 - 8Y2O3, milled with alumina balls, was divided into four portions. Three portions were doped with 2 w/o WC W, and 4 w/o W respectively, in order to simulate contamination during milling. The fourth portion was undoped and used on a control. The addition of W or WC did not affect the phase relationships in the system, as all bars with or without additions contained melilite as the major Si-Y-O-N phase after sintering. At 750 C, instability (rapid oxidation and cracking) of W-doped bars appears to have occurred as a result of oxidation of the tungsten containing melilite phase. No intermediate temperature instability was observed in bars containing 2 w/o WC or in bars with no additive. Specimens exposed at 1350 C had good oxidation resistance due to the formation of a protective siliceous oxide layer. A specimen containing 4 w/o W which was preoxidized at 1350 C had improved oxidation resistance at 750 C. The tendency towards oxidation and cracking of Si3N4 - 8 Y2O3 at 750 C is concluded to be related to tungsten content of the sintered bars.

Schuon, S.↗
NASA NTRS1982

Effect of Y2O3 and Al2O3 on the oxidation resistance of Si3N4

Oxidation of cold-pressed and sintered Si3N4 containing 15 wt% Y2O3 and 2, 4, 6, and 8% Al2O3 is observed at temperatures as low as 1000 C with IR reflection spectroscopy. Concentrations of Al2O3 in excess of 4% greatly retard the rate of oxidation and alter the mechanism of surface attack by promoting formation of a glassy layer on the surface containing mixed oxynitride bonds. The glassy layer retards heterogeneous attack and reduces the effect of an oxidation transition temperature between 1000 and 1100 C for these materials.

Hench, L. L.↗
DOE OSTI2023

Grain boundary enhanced UN and U 3 Si 2 pellets with improved oxidation resistance

A method of forming a water resistant boundary on a fissile material for use in a water cooled nuclear reactor is described. The method comprises mixing a powdered fissile material selected from the group consisting of UN and U3Si2 with an additive selected from oxidation resistant materials having a melting or softening point lower than the sintering temperature of the fissile material, pressing the mixed fissile and additive materials into a pellet, sintering the pellet to a temperature greater than the melting point of the additive. Alternatively, if the melting point of the oxidation resistant particles is greater than the sintering temperature of UN or U3Si2, then the oxidation resistant particles can have a particle size distribution less than that of the UN or U3Si2.

Lahoda, Edward J.↗
NASA NTRS1975

Modified ferritic iron alloys with improved high-temperature mechanical properties and oxidation resistance

An alloy modification program was conducted in which the compositions of two existing Fe-Cr-Al alloys (Armco 18SR and GE-1541) were changed to achieve either improved high-temperature strength or improved fabricability. Only modifications of Armco 18SR were successful in achieving increased strength without loss of fabricability or oxidation resistance. The best modified alloy, designated NASA-18T, had twice the rupture strength of Armco 18SR at 800 and 1000 C. The NASA-18T alloy also had better oxidation resistance than Armco 18SR and comparable fabricability. The nominal composition of NASA-18T is Fe-18Cr-2Al-1Si-1.25Ta. All attempted modifications of the GE-1541 alloy were unsuccessful in terms of achieving better fabricability without sacrificing high-temperature strength and oxidation resistance.

Oldrieve, R. E.↗
DOE OSTI2021

Grain boundary enhanced UN and U3Si2 pellets with improved oxidation resistance

A method of forming a water resistant boundary on a fissile material for use in a water cooled nuclear reactor is described. The method comprises mixing a powdered fissile material selected from the group consisting of UN and U 3 Si 2 with an additive selected from oxidation resistant materials having a melting or softening point lower than the sintering temperature of the fissile material, pressing the mixed fissile and additive materials into a pellet, sintering the pellet to a temperature greater than the melting point of the additive. Alternatively, if the melting point of the oxidation resistant particles is greater than the sintering temperature of UN or U 3 Si 2 , then the oxidation resistant particles can have a particle size distribution less than that of the UN or U 3 Si 2 .

Lahoda, Edward J.↗
NASA NTRS1977

Oxidation-resistant cermet

Chromium metal alloys and chromium oxide ceramic are combined to produce cermets with oxidation-resistant properties. Application of cermets includes use in hot corrosive environments requiring strong resistive materials.

Phillips, W. M.↗
NASA NTRS1972

Improved oxidation-resistant carbon and graphite materials

A variety of silicon-carbide treated carbon and graphite products were prepared, and oxidation and strength properties determined. Carbon and graphite materials used in the preliminary study include fiber, tape, felt, foam, bulk, and laminar configurations. The silicon-carbide treatment used in preparing the oxidation resistant specimens employs either vacuum or ultrasonic impregnation of various silicone-silicon mixtures into the matrix material. The impregnation phase is followed by controlled thermal reaction at which time the silicon carbide is synthesized and takes the form of an integral protective boundary layer. Thickness of the layer ranges from a fraction of a mil to 10 mils, depending on the matrix material and processing parameters. Oxidation resistance of all the silicon-carbide-treated specimens investigated was found to be significantly improved. Mechanical strengths of the laminar composites were also found to be somewhat improved. At room temperature the specific strength of the silicon-carbide treated fibers and tapes was degraded to some extent; however, their relative strengths were significantly increased at elevated temperatures in oxidizing atmosphere.

Muir, H. M.↗
NASA NTRS2001

The Effect of Hydrogen Annealing on the Oxidation Resistance of Four EPM Single Crystal Superalloys

Four single crystal EPM (enabling propulsion materials) developmental airfoil superalloys were hydrogen annealed at 1300 C for up to 100 hours to remove sulfur and improve oxidation resistance. Although the 1100 and 1150 C cyclic oxidation resistance was remarkably improved by annealing for 24 or 100 hours, the behavior was still considerably inferior to that of commercially available single crystal superalloys, especially those that are either Y-doped or hydrogen annealed. Excessive degradation in the developmental alloys appeared to be correlated with low Cr contents and, to a lesser extent, high Co and Re contents.

Smialek, James L.↗
NASA NTRS1990

Cyclic oxidation resistance of a reaction milled NiAl-AlN composite

Based upon recent mechanical property tests a NiAl-AlN composite produced by cryomilling has very attractive high temperature strength. This paper focuses on the oxidation resistance of the NiAl-AlN composite at 1473 and 1573 K as compared to that of Ni-47Al-0.15Zr, one of the most oxidation resistant intermetallics. The results of cyclic oxidation tests show that the NiAl-AlN composite has excellent properties although not quite as good as those of Ni-47Al-0.15Zr. The onset of failure of the NiAl-AlN was unique in that it was not accompanied by a change in scale composition from alumina to less protective oxides. Failure in the composite appears to be related to the entrapment of AlN particles within the alumina scale.

Lowell, Carl E.↗
NASA NTRS1981

Silicon carbide as an oxidation-resistant high-temperature material. 1: Oxidation and heat corrosion behavior

The oxidation and corrosion behavior of SiC (in the form of a SiC powder) and hot-pressed and reaction-bound material were studied. The excellent stability of SiC in an oxidizing atmosphere is due to the development of protective SiO2 coatings. Any changes in these protective layers (e.g., due to impurities, reaction with corrosive media, high porosity of SiC, etc.) lead in most cases to increased rates of oxidation and thus restrict the field of SiC application.

Schlichting, J.↗
NASA NTRS1992

The cyclic oxidation resistance at 1200 C of beta-NiAl, FeAl, and CoAl alloys with selected third element additions

The intermetallic compounds Beta-NiAl, FeAl, and CoAl were tested in cyclic oxidation with selected third element alloy additions. Tests in static air for 200 1-hr cycles at 1200 C indicated by specific weight change/time data and x-ray diffraction analysis that the 5 at percent alloy additions did not significantly improve the oxidation resistance over the alumina forming baseline alloys without the additions. Many of the alloy additions were actually deleterious. Ta and Nb were the only alloy additions that actually altered the nature of the oxide(s) formed and still maintained the oxidation resistance of the protective alumina scale.

Barrett, C. A.↗