Determination of fatigue crack growth in incoloy alloy 800 in molten nitrate salt
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The authors wish to thank C. W. Wilson and J. M. Nobbs for performing the chemical analyses.
REFERENCES 1. B. Chicco and W.R. Thorpe: Metall. Trans. A, 1982, vol. 13A, pp. 1293-97. 2. J. Chipman: in Metals Handbook, 8th ed., ASM, Metals Park, OH, 1973, vol. 8, p. 277. 3. M.G. Benz and J.F. Elliott: Trans. TMS-AIME, 1961, vol. 221, pp. 323-31 and p. 888. 4. R.A. Buckley and W. Hume-Rothery: (a) J. Iron Steel Inst., 1960, vol. 196, pp. 403-06; (b) ibid, 1962, vol. 200, pp. 142-43. 5. S. Ban-ya, J. E Elliott, and J. Chipman: Metall. Trans., 1970, vol. 1, pp. 1313-20. 6. R.L. Orr and J. Chipman: Trans. TMS-AIME, 1967, vol. 239, pp. 630-33. 7. N.R. Draper and H. Smith: Applied Regression Analysis, John Wiley & Sons, New York, NY, 1966, pp. 142-216. 8. R.P. Smith: Trans. TMS-A1ME, 1959, vol. 215, pp. 954-57. 9. E. Scheil, T. Schmidt, and J. Wiinning: Arch. Eisenhiinenw., 1961, vol. 32, pp. 251-60. 10. R.W. Gurry: Trans. A1ME, 1942, vol. 150, pp. 147-53.
storage fluid. While there is some industrial experience with the storage, handling, and containment of these salts, ~ the information available concerns situations involving temperatures well below 600 ~ It becomes important, therefore, to examine the corrosion compatibility of the fluid containment alloy with these nitrate-based salts at temperatures more representative of the operating conditions of SCR facilities. When the heat transfer fluid in an SCR design is a condensed phase, there is no appreciable internal pressurization within the receiver tubes. The mechanical loads of primary interest are therefore thermally induced due to nonuniform heating of the receiver tube panel array. As a result of diurnal insulation and intermittent cloud cover, these loads are cyclic in nature. Characterizing the influence of the salt environment on the fatigue crack growth rate (FCGR) of the alloy is therefore an appropriate experiment in order to determine, at least in one specific way, the susceptibility of Alloy 800 to environmental degradation. In order to determine the effect of environment on crack growth rate in the alloy, it is necessary to know at any time during a test the current crack length, a, and the corresponding stress intensity amplitude, AK. Because specimens were immersed in an opaque, conductive fluid environment for the molten salt tests, it was not possible to use the methods which have been previously employed to measure crack lengths in other high temperature studies, such as visual observations or potential drop measurements. Therefore, a compliance technique based upon the unique relationship between crack length and specimen compliance was used to monitor fatigue crack growth. As given by Ryder et al:2
a / W = exp(-Z ~) where
z
Determination of Fatigue Crack Growth in Incoloy Alloy 800 in Molten Nitrate Salt S.H. GOODS Incoloy Alloy 800 has found wide application as a structural material in both the nuclear and fossil power generating industries as well as in other high temperature applications. Because of its superior corrosion resistance and high
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