ESCA study of oxidation and hot corrosion of nickel-base superalloys |
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| Authors: | S. R. Smith W. J. Carter III G. D. Mateescu F. J. Kohl G. C. Fryburg C. A. Stearns |
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| Affiliation: | (1) Department of Chemistry-MAIF, Case Western Reserve University, Cleveland, Ohio;(2) NASA Lewis Research Center, Cleveland, Ohio |
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| Abstract: | A study of the high-temperature oxidation and Na2SO4-induced hot corrosion of some 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. Oxidation times ranged from 0.5 to 100 hr. Hot corrosion of B-1900 was induced by applying a coating of Na2SO2 to preoxidized samples, then heating to 900° C in slowly flowing O2. Corrosion times ranged from 5 min to 29 hr. For oxidized samples, the predominant type of scale formed by each superalloy was readily determined, and a marked surface enrichment of Ti was found in each case. For corroded samples, the transfer of significant amounts of material from the oxide layer to the surface of the salt layer was observed to occur long before the onset of rapidly accelerating weight gain. Some marked changes in surface composition were observed to coincide 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. Supported by NASA Grant No. NSG-3009 |
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| Keywords: | oxidation hot corrosion ESCA superalloys sodium sulfate |
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