Stress Corrosion Cracking of Inconel Alloys and Weldments in High-Temperature Water — the Effect of Sulfuric Acid Addition

The stress corrosion cracking (SCC) susceptibilities of Alloys 600 and 690, AISI 316 NG stainless steel (SS), ASTM A508 carbon steel, and a number of compatible weld metals have been evaluated at 288 C in pure water and in pure water containing sulfuric acid additions. The sulfuric acid was added to simulate the effects of a resin release from the demineralizer system of a boiling water reactor (BWR). A combination of creviced and noncreviced slow strain rate, constant load, and crack growth rate tests were used in the evaluation. The results indicated that all of the alloys tested in the uncreviced condition were immune to cracking in the pure water environment. The presence of crevices in the pure water environment produced a susceptibility to SCC in Alloy 600, in Inconel I-82 and I-182 weld metals, and ASTM A508 steel, but not in Alloy 690. Cracking was enhanced by the addition of 1 ppm H2SO4 in slow strain rate tests (SSRTs) and constant load tests, but crack growth rates were not enhanced. All of the alloys tested in the resin intrusion environment were susceptible to cracking, except for the high chromium weld metals R-135 and Inconel I-72.