The effects of sulfate impurities in 2880C water on IGSCC OF INCONEL 600 in constant load and SSRT experiments

Constant load and slow strain rate tests (SSRT) were used to determine the effect of heat treatment and sulfuric acid additions on the intergranular stress corrosion cracking susceptibility of three heats of Inconel 600 in 2880C water containing 0.2 ppm oxygen. Compared to pure water, time to failure in constant load tests was decreased by 2 to 3 orders of magnitude in impure water, with failure observed at stresses below yield. IGSCC readily occurred in SSRT experiments at 1.7 x 10-7/s, with many specimens exhibiting 100% intergranular fracture. Susceptibility was generally enhanced by sensitization heat treatments, although failure was observed in three different heats in the mill annealed condition. Properly performed solution annealing apparently eliminated cracking susceptibility. Results correlated with carbide distribution and chromium depletion measurements on these heats performed in another investigation