The Relation Between the Resistance of IGA and IGSCC and the Chromium Depletion of Alloy 690

Abstract The influence of heat treatments on the intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC) resistance of lnconel 690 (UNS N06690) were studied. The chromium profiles adjacent to the grain boundary were predicted by thermodynamic and kinetic modeling and benchmarked with experimental results. The relative susceptibilities of alloy 690 with various heat treatments to stress corrosion cracking (SCC) in 0.001 M Na2S2O3 and low pH at room temperature were evaluated. The results of slow strain rate tensile (SSRT) testing showed good IGSCC resistance of alloy 690. The results of the Huey test showed very little weight loss for various heat treatments. The good resistance of IGA and IGSCC for alloy 690 are considered to be attributed to the higher equilibrium chromium concentration at the intergranular carbide–matrix interface.