Several nickel-base superalloy (UNS N06600) welded heat-exchanger tubes used in processing black liquor in a kraft paper mill failed prematurely. Leaking occurred through the tube walls at levels near the bottom tube sheet. The tubes had been installed as replacements for type 304 stainless steel tubes. Visual and stereoscopic examination revealed three types of corrosion on the inside surfaces of the tubes: uniform attack, deeper localized corrosive attack, and accelerated uniform attack. Metallographic analysis indicated that pronounced dissimilar-metal corrosion had occurred in the base metal immediately adjacent to the weld seam. The corrosion was attributed to exposure to nitric...
J. Robert Kattus, Failure of Nickel-Base Superalloy Heat-Exchanger Tubes in a Black Liquor Heater, Handbook of Case Histories in Failure Analysis, Vol 2, Edited By Khlefa A. Esaklul, ASM International, 1993, p 95–98, https://doi.org/10.31399/asm.fach.v02.c9001311
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