Stress Corrosion Cracking of Alloys 600 and 690 and Nos. 82 and 182 Weld Metals in High Temperature Water

The relative susceptibilities of Alloy 600 and 690 base metals and I-82 and I-182 weld metals to intergranular stress corrosion cracking (IGSCC) in pure water at 288 C were evaluated. A combination of creviced and noncreviced slow strain rate, smooth sustained load, and precracked fracture mechanics tests were employed in the evaluation. Susceptibility was determined as a function of dissolved oxygen content, degree of sensitization, and crevice condition. The results indicated that Alloy 600, and I-182 and I-82 weld metals were susceptible to various degrees of IGSCC in oxygen containing pure water when creviced, and immune to IGSCC when uncreviced. Alloy 690 was immune to IGSCC under all conditions examined. In Alloy 600, no correlation was found between the location of IGSCC and the location of maximum sensitization as determined by a boiling 25% nitric acid test and an electrolytic 8:1 phosphoric acid etch.