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  • 1
    Publication Date: 2013-08-31
    Description: The susceptibility to hot corrosion of four nickel-base, cast superalloys has been studied at 900 and 1000 C. The test consisted of coating alloy samples with known amounts of Na2SO4 and oxidizing the coated samples isothermally in 1 atmosphere of slowly flowing oxygen, the weight-gain being monitored on a sensitive recording microbalance. Susceptibility to hot corrosion decreased in the order of decreasing molybdenum content of the alloys. Preoxidation of samples before hot-corrosion testing markedly increased the induction period observed prior to the inception of hot corrosion for all alloys tested. X-ray diffraction analyses of the oxide scales were made. All samples that underwent hot corrosion showed the presence of a (Ni,Co)MoO4 layer near the alloy-oxide interface. Several specimens displayed resistance to hot corrosion and these showed NaTaO3 as a prominent feature in their oxide scale. Our results may be interpreted as indicating that molybdenum in an alloy is detrimental, with respect to hot corrosion, while tantalum is beneficial.
    Keywords: METALLIC MATERIALS
    Type: NASA-TN-D-8461 , E-8977
    Format: application/pdf
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  • 2
    Publication Date: 2013-08-31
    Description: The oxidation at 900 and 1,000 C of four nickel-base superalloys in 1 atmosphere of slowly flowing oxygen was investigated. Thermogravimetric rate data were obtained for periods to 100 hours. The morphology and composition of the oxide scales formed after 100 hours were studied by optical microscopy, X-ray diffraction, electron microprobe, scanning electron microscopy, and X-ray photoelectron spectroscopy (ESCA). Alloys B-1900 and VIA were found to be primarily alumina formers, though probably 25 percent of their surface was covered by CR2O3-containing oxides at 900 C. Alloys 713C and IN-738 were primarily chromia formers, though the surface of 713C at 1,000 C was covered with NiO, and the surface of IN-738 at both temperatures was covered with a thin layer of TiO2.
    Keywords: METALLIC MATERIALS
    Type: E-8770 , NASA-TN-D-8388
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  • 3
    Publication Date: 2013-08-31
    Description: Mass spectrometric and target collection experiments were made at 1600 K to elucidate the mode of oxidative vaporization of two columbium alloys, fused-slurry-coated with a complex silicide former (Si-20Cr-Fe). At oxygen pressures up to 0.0005 torr the major vapor component detected by mass spectrometry for oxidized samples was gaseous silicon monoxide. Analysis of condensates collected at oxygen pressures of 0.1, 1.0 and 10 torr revealed that chromium-, silicon-, iron- and tungsten- containing species were the major products of vaporization. Equilibrium thermochemical diagrams were constructed for the metal-oxygen system corresponding to each constituent metal in both the coating and base alloy. The major vaporizing species are expected to be the gaseous oxides of chromium, silicon, iron and tungsten. Plots of vapor phase composition and maximum vaporization rate versus oxygen pressure were calculated for each coating constituent. The major contribution to weight loss by vaporization at oxygen pressures above 1 torr was shown to be the chromium-containing species.
    Keywords: MATERIALS, METALLIC
    Type: NASA-TM-X-67980 , E-6704
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  • 4
    Publication Date: 2013-08-31
    Description: Knudsen flow mass spectrometry, thermodynamics, and chemical bonding of titanium, zirconium, hafnium, and thorium carbides during high temperature vaporization
    Keywords: MATERIALS, METALLIC
    Type: NASA-TM-X-67844
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  • 5
    Publication Date: 2013-08-31
    Description: Studying vaporization of indium-gallium oxide, and gallium-aluminum oxide by Knudsen effusion mass spectroscopy
    Keywords: CHEMISTRY
    Type: E-6140 , NASA-TN-D-6318
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  • 6
    Publication Date: 2013-08-31
    Description: Mass spectroscopy of vaporization of lanthanum and scandium carbides
    Keywords: MATERIALS, METALLIC
    Type: NASA-TN-D-7039 , E-5865
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  • 7
    Publication Date: 2013-08-31
    Description: Dissociation energy of gaseous titanium nitride
    Keywords: CHEMISTRY
    Type: NASA-TN-D-5027
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  • 8
    Publication Date: 2013-08-31
    Description: Wedge shaped specimens were exposed to the combustion gases of a Mach 0.3 burner rig fueled with a mixture of 40 weight percent micron size coal particles dispersed in No. 2 fuel oil. Exposure temperature was about 900 C and the test duration was about 44 one hour cycles. The alloys tested were the nickel base superalloys, IN-100, U-700 and IN-792, and the cobalt base superalloy, Mar-M509. The deposits on the specimens were analyzed and the extent of corrosion/erosion was measured. The chemical compositions of the deposits were compared with the predictions from an equilibrium thermodynamic analysis. The experimental results were in very good agreement with the predictions.
    Keywords: METALLIC MATERIALS
    Type: DOE/NASA/2593-23 , NASA-TM-81686 , E-718
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  • 9
    Publication Date: 2013-08-31
    Description: Results are presented for recent analytical and experimental studies of the role of K2S in MHD hot stream seed recovery. The existing thermodynamic data base was found to contain large uncertainties and to be nonexistent for vapor phase K2S. Knudsen cell mass spectrometric experiments were undertaken to determine the vapor species in equilibrium with K2S(c). K atoms and S2 molecules ere found to be the major vapor phase species in vacuum, accounting for greater than 99 percent of the vapor phase. Combustion gas deposition studies using No. 2 Diesel fuel were also undertaken and revealed that condensed phase K2SO3 may potentially be an important compound in the MHD stream at near-stoichiometric combustion.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: E-9948 , DOE/NASA/2674-79/1 , NASA-TM-79114
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  • 10
    Publication Date: 2013-08-31
    Description: Sodium-sulfate-induced hot corrosion of preoxidized IN-738 was studied at 975 C with special emphasis placed on the processes occurring during the long induction period. Thermogravimetric tests were run for predetermined periods of time, and then one set of specimens was washed with water. Chemical analysis of the wash solutions yielded information about water soluble metal salts and residual sulfate. A second set of samples was cross sectioned dry and polished in a nonaqueous medium. Element distributions within the oxide scale were obtained from electron microprobe X-ray micrographs. Evolution of SO was monitored throughout the thermogravimetric tests. Kinetic rate studies were performed for several pertinent processes; appropriate rate constants were obtained from the following chemical reactions: Cr2O3 + 2 Na2SO4(1) + 3/2 O2 yields 2 Na2CrO4(1) + 2 SO3(g)n TiO2 + Na2SO4(1) yields Na2O(TiO2)n + SO3(g)n TiO2 + Na2CrO4(1) yields Na2O(TiO2)n + CrO3(g).
    Keywords: METALLIC MATERIALS
    Type: NASA-TP-2319 , NAS 1.60:2319 , E-1847
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