Abstract
The influence of the electrode potential on the corrosion behavior of a series of Ni-base superalloys has been investigated in a (mole %) 90Na2SO4-10K2SO4 melt at 1173 K. Acidic fluxing occurs at positive potentials and basic fluxing at negative potentials. A protective scale is formed in an intermediate (neutral) potential range on high chromium-containing alloys such as IN-738LC, IN-939, IN-597, and IN-657. The breakthrough potentials for acidic and basic fluxing depend on the composition of the alloy. Alloys with low chromium contents such as IN-100 and IN-713LC do not form stable protective scales at any potential. Numerous sulfide phases have been identified in the scale and subscale, depending on potential, severity of attack, and material composition. NaCrS2 only forms under basic fluxing conditions. Its presence can therefore be considered as an indication that basic fluxing conditions have existed.
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References
A. Rahmel, M. Schmidt, and M. Schorr,Oxid. Met. 18, 195 (1982).
A. Rahmel,Electrochim. Acta 21, 853 (1976).
E. Tatar-Moisescu and A. Rahmel,Electrochim. Acta 20, 479 (1975).
A. Rahmel,Werkst. Korros. 19, 750 (1968).
R. A. Rapp and K. S. Goto, inSecond International Symposium on Molten Salts, G. Braunstein and R. Selmanm eds. (The Electrochemical Society, Princeton, 1979).
D. K. Gupta and R. A. Rapp,J. Electrochem. Soc. 127, 2194 (1980).
W. P. Stroud and R. A. Rapp, inHigh Temperature Metal Halide Chemistry, D. L. Hildenbrand and D. D. Cubicciotti, eds. (The Electrochemical Society, Princeton, 1978). p. 574.
W. T. Wu, A. Rahmel and M. Schmidt,Electrochim. Acta in press.
H.-E. Bühler and H. P. Hougardy,Atlas of Interference Layer Metallography (Deutsche Gesellschaft für Metallkunde, Oberursel, 1980). (Also available from the American Society of Metals and the Metals Society).
E. Erdös, inDeposition and Corrosion in Gas Turbines, A. B. Hart and A. J. B. Cutler, eds. (Applied Science Publishers, London, 1973), p. 115.
W. T. Wu, I. Aydin, and H.-E. Bühler,Prakt. Metallogr. 19, 322 (1982).
E. Erdös, A. Rahmel, M. Schmidt, M. Schorr, and W. T. Wu,Oxid. Met. 18, 187 (1982).
J. F. G. Condé, E. Erdös, and A. Rahmel, inHigh Temperature Alloys for Gas Turbines 1982, R. Brunetaud, D. Coutsouradis, T. B. Gibbons, Y. Lindblom, D. B. Meadowcroft and R. Stickler, eds. (D. Reidel, Dordrecht, Holland, 1982), p. 99.
E. Erdös, H. Altorfer, and E. Denzler,Werkst. Korros. 33, 373 (1982).
W. T. Wu, A. Rahmel, and M. Schorr, to be published.
G. C. Fryburg, F. J. Kohl, C. A. Stearns, and W. L. Fielder,J. Electrochem. Soc. 129, 571 (1982).
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Wu, W.T., Rahmel, A. & Schorr, M. Acidic and basic fluxing of Ni-base superalloys in a 90Na2SO4-10K2SO4 melt at 1173 K. Oxid Met 19, 201–229 (1983). https://doi.org/10.1007/BF00666645
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DOI: https://doi.org/10.1007/BF00666645