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  • 1
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    Chemical reactions involved in the initiation of hot corrosion of IN-738 (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    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; Cr203 + 2 Na2S04(1) + 3/2 02 yields 2 Na2Cr04(1) + 2 S03(g)n TiO2 + Na2S04(1) yields Na20(T102)n + 503(g)n T102 + Na2Cro4(1) yields Na2(T102)n + Cr03(g).
    Keywords: METALLIC MATERIALS
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 131; 2985-299
    Format: text
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  • 2
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    Mechanism of beneficial effect of tantalum in hot corrosion of nickel-base superalloys (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: X-ray diffraction and electron microprobe analyses were used to examine a prominent NaTaO3 pattern formed in a number of nickel-base superalloys. It is found that a beneficial effect of tantalum with respect to hot corrosion attack arises from the ability of Ta2O5 to tie up Na2O and prevent the formation of a molten Na2MoO4 phase.
    Keywords: METALLIC MATERIALS
    Type: Electrochemical Society; vol. 124
    Format: text
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  • 3
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    Chemical mechanisms and reaction rates for the initiation of hot corrosion of IN-738 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    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 , E-1847 , NAS 1.60:2319
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  • 4
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    ESCA study of oxidation and hot corrosion of nickel-base superalloys (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A study of the high-temperature oxidation and Na2SO4-induced hot corrosion of nickel-base superalloys has been accomplished by using ESCA to determine the surface composition of the oxidized or corroded samples. Oxidation was carried out at 900 or 1000 C in slowly flowing O2 for samples of B-1900, NASA-TRW VIA, 713C, and IN-738. Hot corrosion of B-1900 was induced by applying a coating of Na2SO4 to preoxidized samples, then heating to 900 C in slowly flowing O2. For oxidized samples, the predominant type of scale formed by each superalloy showed a marked surface enrichment of Ti. For corroded samples, the transfer of significant amounts of material from the oxide layer to the surface of the salt layer was observed before the onset of rapidly accelerating weight gain. Marked changes in surface composition coincided with the beginning of accelerating corrosion, the most striking of which were a tenfold decrease in the sulfur to sodium ratio and an increase in the Cr(VI) to Cr(III) ratio.
    Keywords: METALLIC MATERIALS
    Type: Oxidation of Metals; 14; Oct. 198
    Format: text
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  • 5
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    Deposition and material response from Mach 0.3 burner rig combustion of SRC 2 fuels (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Collectors at 1173K (900 C) were exposed to the combustion products of a Mach 0.3 burner rig fueled with various industrial turbine liquid fuels from solvent refined coals. Four fuels were employed: a naphtha, a light oil, a wash solvent and a mid-heavy distillate blend. The response of four superalloys (IN-100, U 700, IN 792 and M-509) to exposure to the combustion gases from the SRC-2 naphtha and resultant deposits was also determined. The SRC-2 fuel analysis and insights obtained during the combustion experience are discussed. Particular problems encountered were fuel instability and reactions of the fuel with hardware components. The major metallic elements which contributed to the deposits were copper, iron, chromium, calcium, aluminum, nickel, silicon, titanium, zinc, and sodium. The deposits were found to be mainly metal oxides. An equilibrium thermodynamic analysis was employed to predict the chemical composition of the deposits. The agreement between the predicted and observed compounds was excellent. No hot corrosion was observed. This was expected because the deposits contained very little sodium or potassium and consisted mainly of the unreactive oxides. However, the amounts of deposits formed indicated that fouling is a potential problem with the use of these fuels.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-81634 , E-647 , DOE/NASA/2593-20
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  • 6
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    Material response from Mach 0.3 burner rig combustion of a coal-oil mixture (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    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: NASA-TM-81686 , DOE/NASA/2593-23 , E-718
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  • 7
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    The effect of fuel-to-air ratio on burner-rig hot corrosion (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Samples of a cobalt-base alloy, Mar M-509, were subjected to hot corrosion in a Mach-0.3 burner rig. The corrodent was NaCl added as an aqueous solution to the combustion products of a sulfur-containing Jet-A fuel. The metal temperature was fixed at 900 C. The extent of hot corrosion increased by a factor of three as the fuel-to-air mass ratio was increased from 0.033 to 0.050. Because the depositing salt was always Na2SO4, the increased attack appeared to be related to the gas composition.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-78960 , E-9649
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  • 8
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    Chemical processes involved in the initiation of hot corrosion of B-1900 and NASA-TRW VIA (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Sodium sulfate induced hot corrosion of B-1900 and NASA-TRW VIA at 900 C was studied with special emphasis on the chemical reactions occurring during and immediately after the induction period. Thermogravimetric tests were run for set periods of time after which the samples were washed with water and water soluable metal salts and/or residual sulfates were analyzed chemically. Element distributions within the oxide layer were obtained from electron microprobe X-ray micrographs. A third set of samples were subjected to surface analysis by X-ray photoelectron spectroscopy. Evolution of SO2 was monitored throughout many of the hot corrosion tests. Results are interpreted in terms of acid-base fluxing mechanisms.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-81399 , E-308 , Meeting of the Electrochem. Soc.; Oct 14, 1979 - Oct 19, 1979; Los Angeles
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  • 9
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    Thermochemical analyses of the oxidative vaporization of metals and oxides by oxygen molecules and atoms (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Equilibrium thermochemical analyses are employed to describe the vaporization processes of metals and metal oxides upon exposure to molecular and atomic oxygen. Specific analytic results for the chromium-, platinum-, aluminum-, and silicon-oxygen systems are presented. Maximum rates of oxidative vaporization predicted from the thermochemical considerations are compared with experimental results for chromium and platinum. The oxidative vaporization rates of chromium and platinum are considerably enhanced by oxygen atoms.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-X-73682 , E-9032 , Symp. on Corrosion Problems Involving Volatile Corrosion Products; May 08, 1977 - May 13, 1977; Philadelphia
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  • 10
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    Gaseous sodium sulfate formation in flames and flowing gas environments (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Formation of Na2SO4(g) in flames and hot flowing gas systems was studied by high pressure, free-jet expansion, modulated molecular beam mass spectrometric sampling. Fuel-lean CH4-O2 flames doped with SO2, H2O and NaCl yielded the gaseous Na2SO4 molecule in residence times of less than one millisecond. Intermediate species NaSO2(g) and NaSO3(g) were also observed and measured. Composition profiles were obtained for all reaction products. Nonflame flowing gas experiments showed that Na2SO4 and NaSO3 gaseous molecules were formed at 1140 C in mixtures of O2, H2O(g), SO2 and NaCl(g). Experimental results are compared with calculated equilibrium thermodynamic predictions.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-X-73600 , E-9029 , Symp. on Corrosion Probl. Involving Volatile Corrosion Products; May 08, 1977 - May 13, 1977; Philadelphia
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