Search NASA⌕ Search

Engineering topics

Sanders, W. A.

Publications and source records attributed to Sanders, W. A..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Effect of thermal cycling in a Mach 0.3 burner rig on properties and structure of directionally solidified gamma/gamma prime - delta eutectic

Tensile and stress rupture properties at 1040 C of a thermally cycled gamma/gamma prime - delta eutectic were essentially equivalent to the as-grown properties. Tensile strength and rupture life at 760 C appeared to decrease slightly by thermal cycling. Thermal cycling resulted in gamma prime coarsening and Widmanstatten delta precipitation in the gamma phase. An unidentified precipitate, presumably gamma prime, was observed within the delta phase. The eutectic alloy exhibited a high rate of oxidation-erosion weight loss during thermal cycling in the Mach 0.3 burner rig.

Gray, H. R.↗
NASA NTRS1975

Silicon nitride-aluminum oxide solid solution (SiAION) formation and densification by pressure sintering

Stirred-ball-mill-blended Si3N4 and Al2O3 powders were pressure sintered in order to investigate the mechanism of solid solution formation and densification in the Si3N4-Al2O3 system. Powder blends with Si3N4:Al2O3 mole ratios of 4:1, 3:2, and 2:3 were pressure sintered at 27.6-MN/sq m pressure at temperatures to 17000 C (3090 F). The compaction behavior of the powder blends during pressure sintering was determined by observing the density of the powder compact as a function of temperature and time starting from room temperature. This information, combined with the results of X-ray diffraction and metallographic analyses regarding solutioning and phase transformation phenomena in the Si3N4-Al2O3 system, was used to describe the densification behavior.

Yeh, H. C.↗
NASA NTRS1974

Dynamic oxidation behavior at 1000 and 1100 C of four nickel-base cast alloys, NASA-TRW VIA, B-1900, 713C, and 738X

The superalloys NASA-TRW VIA, B-1900, 713C, and 738X were tested cyclically and isothermally for resistance to oxidation in high velocity gas streams for 100 hours at specimen temperatures of 1000 C and 1100 C. Alloys VIA and B-1900, which were the most oxidation resistant, displayed slight and very similar weight changes and metal losses. Alloy 713C also sustained only slight metal losses, but it exhibited some tendency to spall. Alloy 738X was found to be the most susceptible to cyclic oxidation; this resulted in heavy spalling, which in turn caused high weight losses and high metal losses. Oxidation test results are related to the amounts of chromium aluminum, and the refractory metals in the alloys investigated.

Sanders, W. A.↗
NASA NTRS1974

Behavior of ceramics at 1200 C in a simulated gas turbine environment

This report summarizes programs at the NASA Lewis Research Center evaluating several classes of commercial ceramics, in a high gas velocity burner rig simulating a gas turbine engine environment. Testing of 23 ceramics in rod geometry identified SiC and Si3N4 as outstanding in resistance to oxidation and thermal stress and identified the failure modes of other ceramics. Further testing of a group of 15 types of SiC and Si3N4 in simulated vane shape geometry has identified a hot pressed SiC, a reaction sintered SiC, and hot pressed Si3N4 as the best of that group. SiC and Si3N4 test specimens were compared on the basis of weight change, dimensional reductions, metallography, fluorescent penetrant inspection, X-ray diffraction analyses, and failure mode.

Sanders, W. A.↗
NASA NTRS1974

High gas velocity burner tests on silicon carbide and silicon nitride at 1200 C

Ten SiC materials and five Si3N4 materials were exposed in a Mach 1-gas-velocity burner simulating a gas-turbine engine environment. All materials studied are commercially available. Cyclic tests up to 100 hours' duration were conducted at specimen temperatures of 1200 C. A specimen geometry was used that develops thermal stresses during thermal cycling in a manner similar to blades and vanes of a gas turbine engine. Materials were compared on a basis of weight change, dimensional reductions, metallography, fluorescent-penetrant inspection, X-ray diffraction analyses, failure mode, and general appearance. One hot-pressed SiC, one reaction-sintered SiC, and three hot-pressed Si3N4 materials survived the program goal of 100 one-hour cycles of exposures. Of the materials that failed to meet the program goal, thermal fatigue was identified as the exclusive failure mode.

Sanders, W. A.↗
NASA NTRS1973

High gas velocity burner tests on silicon carbide and silicon nitride at 1200 C

Specimens of silicon carbide and silicon nitride were exposed to a Mach one gas velocity burner simulating a turbine engine environment. Cyclic tests up to 100 hour duration were conducted at specimen temperatures of 1200 C. A specimen geometry was used that develops thermal stresses during thermal cycling in a manner similar to blades and vanes of a gas turbine engine. Materials were compared on a basis of weight change, dimensional reductions, metallography, fluorescent penetrant inspection, X-ray diffraction analyses, failure mode, and general appearance. One hot pressed SiC, one reaction sintered SiC, and three hot pressed Si3N4 specimens survived the program goal of 100 one-hour cycle exposures. Of the materials that failed to meet the program goal, thermal fatigue was identified as the exclusive failure mode.

Sanders, W. A.↗
NASA NTRS1972

Mach 1 oxidation of thoriated nickel chromium at 1204 C /2200 F/.

Electropolished and ground samples of TD-NiCr were exposed to a 1-atm, Mach 1 gas stream at 1204 C for times up to 50 hr. The samples were subjected to both cyclic and isothermal exposure. Weight change, metal loss, X-ray diffraction, metallographic, and electron microprobe analyses were performed. Neither surface preparation nor cyclic-against-isothermal-exposure conditions had a strong effect on the oxidation behavior of the alloy. Initially, a Cr2O3 layer was formed whose volatilization resulted in a very rapid loss of metal - more than 40 microns in the first hour. At about 1 hr, the Cr2O3 layer broke down and NiO began to cover the surface. By 5 hr, the NiO had covered the surface and the rate of loss slowed. The rate-controlling step was diffusion of Cr through NiO.

Lowell, C. E.↗
NASA NTRS1972

Evaluation of oxidation resistant nonmetallic materials at 1204 C (2200 F) in a Mach 1 burner

Specimens of 23 oxidation resistant, nonmetallic, refractory materials were systematically exposed in a high gas velocity burner to simulate a turbine engine environment. Isothermal and cyclic tests were conducted at a specimen temperature of 2200F which resulted from exposure to Mach 1 or Mach 0.5 hot gas streams. Specimen behavior was judged on the basis of failure mode, appearance, and weight change. SiC and Si3N4 exhibited the most promising behavior surviving all exposures including Mach 1 for 120 cycles (10 hr). Major failure modes identified for other materials were thermal shock, thermal fatigue, and mechanical failure due to gas loading.

Sanders, W. A.↗
NASA NTRS1971

Mach 1 oxidation of thoriated nickel chromium at 1204 C (2200 F)

TD NiCr was exposed to a Mach 1, 1-atmosphere gas stream at 1204 C for times up to 50 hours. Weight change, metal thickness loss, X-ray diffraction, metallographic, and electron microprobe analyses were made. Neither surface preparation nor thermal cycling had an appreciable effect on the results. Initially, Cr2O3 formed and volatilized, allowing a rapid metal loss rate of 40 microns per hour. After about 1 hour the Cr2O3 broke down, resulting in an NiO overgrowth. The metal loss rate then slowed to 2.5 microns per hour and remained constant to 50 hours.

Lowell, C. E.↗
NASA NTRS1971

Oxidation screening at 1204 C /2200 F/ of candidate alloys for the space shuttle thermal protection system.

Evaluation of the oxidation resistance of 15 alloys under some of the environmental conditions that might be encountered by the shuttle thermal protection system. The alloys included nickel-, iron-, and cobalt-base wrought alloys. Specimens were self-resistively heated to 1204 C (2200 F) in a 10-torr still-air environment for 100 thirty-minute cycles. Specimen weight, thickness, and microstructural changes were noted, and surface scales were identified by room-temperature X-ray diffraction. Based on these observations, the behavior of the alloys was evaluated in terms of overall amount of metal consumption due to oxide formation and relative tendency toward oxide spalling and scale vaporization.

Sanders, W. A.↗
NASA NTRS1971

Hot corrosion of TD nickel and TD nickel chromium in a high velocity gas stream.

Results of cyclical tests of TD nickel (2% thoria-dispersed nickel) and TD nickel chromium (2% thoria-dispersed nickel-20% chromium alloy) 1.5 mm (60 mil) sheet specimens for susceptibility to hot corrosion in a Mach 0.5 gas stream of Jet A-1 fuel combustion products containing 2 ppm sea salt. Tests as long as 500 one-hour cycles between room temperature and specimen hot zone temperatures of 899 C (1650 F), 982 C (1800 F), and 1149 C (2100 F) were performed. Evidence of hot corrosion was found for both materials in the 899 C (1650 F) and 982 C (1800 F) tests, but not at 1149 C (2100 F). It was concluded that because of high metal thickness losses neither alloy in sheet form is suitable for long-time engine application in a hot corrosion environment at temperatures of 982 C (1800 F) or above.

Sanders, W. A.↗
NASA NTRS1965

Approximation of expectation values.

Approximation of expectation values for nonenergy properties via perturbation theory, obtaining values for molecular polarizability

POLARIZATION CHARACTERISTICS↗