IGSCC Behavior of Alloy 600 Steam Generator Tubing in Water or Steam Tests Above 360 C

Abstract

Laboratory testing to produce intergranular stress corrosion cracking (IGSCC) of Alloy 600 steam generator tubing in primary water environments can require lengthy exposure times, even at a temperature of 360 C (680 F). Recent testing of Alloy 600 in hydrogen-containing steam at 400 C (750 F) has shown the characteristic IGSCC phenomenology, but with about a tenfold decrease in the IGSCC initiation time compared to the time in high-purity, hydrogen-containing water at 360 C. The IGSCC behavior depends both on the steam pressure/density and the hydrogen partial pressure. The role of microstructural variables, including grain boundary carbide precipitation and heat treatment, is similar in water and steam.