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Results for “OXIDATION RESISTANCE”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Effect of chlorine purification on oxidation resistance of some mechanical carbons

Oxidation experiments were conducted with some experimental and commercial mechanical carbons at 650 C in dry air flowing at 28 cc/sec (STP). In general, purification of these carbon-graphites with chlorine at 2800 C improved oxidation resistance. Additional improvements in oxidation resistance were obtained from purification followed by an antioxidant (zinc phosphate) treatment. For the commercial materials, purification alone gave greater oxidation resistance than the antioxidant treatment alone. The reverse, however, was the case for the experimental materials.

Wisander, D. W.↗
NASA NTRS1982

Development of rapidly solidified oxidation resistant alloys

The development of iron-base alloys that contain low concentrations of expensive and/or strategic metals, but that are very resistant to oxidation at elevated tempratures was investigated. Rapid solidification processing was employed to make alloys that are uniform in composition, that comprise very fine grains 10 microns and that contain a uniform dispersion of very fine ( 0.5 microns) nonmetallic inclusions. Each of these factors contribute to the oxidation behavior of alloys. The compositional and processing variables that yield the optimum oxidation resistance are described.

Yurek, G. J.↗
NASA NTRS1984

Oxidation resistance of silicon ceramics

Oxidation resistance, and examples of oxidation of SiC, Si3N4 and sialon are reviewed. A description is given of the oxidation mechanism, including the oxidation product, oxidation reaction and the bubble size. The oxidation reactions are represented graphically. An assessment is made of the oxidation process, and an oxidation example of silicon ceramics is given.

Yasutoshi, H.↗
NASA NTRS1973

Oxidation resistance of selected mechanical carbons at 650 deg C in dry flowing air

Oxidation experiments were conducted with several experimental mechanical carbons at 650 C in air flowing at 28 cu cm/sec (STP). Experiments indicate that boron carbide addition and zinc phosphate treatment definitely improved oxidation resistance. Impregnation with coal tar pitch before final graphitization had some beneficial effect on oxidation resistance and it markedly improved flexure strength and hardness. Graphitization temperature alone did not affect oxidation resistance, but with enough added boron carbide the oxidation resistance was increased although the hardness greatly decreased.

Allen, G. P.↗
NASA NTRS1975

Improvement in oxidation resistance of the leading edge thermal protection for a space shuttle

To improve the oxidation resistance of a carbon-carbon composite, impregnations were performed using pitches, polyfurfuryl alcohols, and phenolic resins, including a silicon-doped phenolic resin. Oxidation resistance and strength increased for all of the composites as the impregnant-carbon residue increased. The properties of the composites impregnated with the nonsilicon-bearing resins were nearly identical and depended only on the amount of impregnant residue present. However, for equivalent residue concentrations, composites produced with the silicon-bearing resin gave higher strengths and at least 100% better oxidation resistance than was observed for the other composites or for a prototype control material.

Williams, J. M.↗
NASA NTRS1991

Niobium-aluminum base alloys having improved, high temperature oxidation resistance

A niobium-aluminum base alloy having improved oxidation resistance at high temperatures and consisting essentially of 48%-52% niobium, 36%-42% aluminum, 4%-10% chromium, 0%-2%, more preferably 1%-2%, silicon and/or tungsten with tungsten being preferred, and 0.1%-2.0% of a rare earth selected from the group consisting of yttrium, ytterbium and erbium. Parabolic oxidation rates, k.sub.p, at 1200.degree. C. range from about 0.006 to 0.032 (mg/cm.sup.2).sup.2 /hr. The new alloys also exhibit excellent cyclic oxidation resistance.

Hebsur, Mohan G.↗
NASA NTRS1985

Oxidation resistant slurry coating for carbon-based materials

An oxidation resistant coating is produced on carbon-base materials, and the same processing step effects an infiltration of the substrate with silicon containing material. The process comprises making a slurry of nickel and silicon powders in a nitrocellulose lacquer, spraying onto the graphite or carbon-carbon substrate, and sintering in vacuum to form a fused coating that wets and covers the surface as well as penetrates into the pores of the substrate. Optimum wetting and infiltration occurs in the range of Ni-60 w/o Si to Ni-90 w/o Si with deposited thicknesses of 25-100 mg/sq. cm. Sintering temperatures of about 1200 C to about 1400 C are used, depending on the melting point of the specific coating composition. The sintered coating results in Ni-Si intermetallic phases and SiC, both of which are highly oxidation resistant.

Smialek, J. L.↗
NASA NTRS1952

Oxidation-resistance Mechanism and Other Properties of Molybdenum Disilicide

The outstanding oxidation resistance of molybdenum disilicide at 2400 F and above was found to depend on the formation of a protective siliceous coating which a-cristobalie has been identified. Molybdenum disilicide is not inherently resistant to oxidation and in powdered form burns at low temperatures.Melting and casting experiments have demonstrated the decomposition of the material at the melting point. The room-temperature modulus of elasticity has been determined and electric-resistivity data are given to 2000 F.

MATERIALS, PROPERTIES-CORROSION RESISTANCE↗
NASA NTRS2003

High-Temperature Oxidation-Resistant and Low Coefficient of Thermal Expansion NiAl-Base Bond Coat Developed for a Turbine Blade Application

Many critical gas turbine engine components are currently made from Ni-base superalloys that are coated with a thermal barrier coating (TBC). The TBC consists of a ZrO2-based top coat and a bond coat that is used to enhance the bonding between the superalloy substrate and the top coat. MCrAlY alloys (CoCrAlY and NiCrAlY) are currently used as bond coats and are chosen for their very good oxidation resistance. TBC life is frequently limited by the oxidation resistance of the bond coat, along with a thermal expansion mismatch between the metallic bond coat and the ceramic top coat. The aim of this investigation at the NASA Glenn Research Center was to develop a new longer life, higher temperature bond coat by improving both the oxidation resistance and the thermal expansion characteristics of the bond coat. Nickel aluminide (NiAl) has excellent high-temperature oxidation resistance and can sustain a protective Al2O3 scale to longer times and higher temperatures in comparison to MCrAlY alloys. Cryomilling of NiAl results in aluminum nitride (AlN) formation that reduces the coefficient of thermal expansion (CTE) of the alloy and enhances creep strength. Thus, additions of cryomilled NiAl-AlN to CoCrAlY were examined as a potential bond coat. In this work, the composite alloy was investigated as a stand-alone substrate to demonstrate its feasibility prior to actual use as a coating. About 85 percent of prealloyed NiAl and 15 percent of standard commercial CoCrAlY alloys were mixed and cryomilled in an attritor with stainless steel balls used as grinding media. The milling was carried out in the presence of liquid nitrogen. The milled powder was consolidated by hot extrusion or by hot isostatic pressing. From the consolidated material, oxidation coupons, four-point bend, CTE, and tensile specimens were machined. The CTE measurements were made between room temperature and 1000 C in an argon atmosphere. It is shown that the CTE of the NiAl-AlN-CoCrAlY composite bond coat is lower than that of the commercially used coating alloy 16-6. To examine the potential of NiAl-AlN-CoCrAlY as a bond coat, we subjected two samples to cyclic furnace testing. The furnace cycle consisted of 45 min at 1163 C (2125 F ) followed by 15 min of cooling out of the furnace. The current NASA baseline TBC is a NiCrAlY bond coat below the 7YSZ top coat. The average TBC life for this baseline coating on Ren N5 is 188 plus or minus 19 cycles. NiAl-AlN-CoCrAlY specimens coated with the same 7YSZ top coat were still intact even after 1000 cycles. Therefore, the NiAl-AlN-CoCrAlY as a bulk substrate material, exhibits more than 5 times the life of the current state-of-the-art material. The next step is to evaluate this material as a coating on the same superalloy substrate.

Source record↗
NASA NTRS1996

Designing Ni- and Co-Base Superalloys To Resist Oxidation

Analysis of experimental cyclic-oxidation data yields quantitative design criterion. Equation characterizing abilities of superalloys to resist oxidation at high temperatures proves useful for designing new alloy compositions to resist oxidation. Rates tendency to become oxidized in terms of single attack parameter, K(a), as function of composition and temperature: decrease in K(a) signifies increase in resistance to oxidation.

Barrett, Charles A.↗
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.↗
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.↗