Stress corrosion crack growth behavior of precipitation hardening martensitic stainless steel in simulated BWR environment

Abstract

Precipitation hardening martensitic stainless steel SUS630 (equivalent to 17-4 PH) has been used for valve stems in light water reactors, because of its high strength and good corrosion resistance. SUS630 is known to be susceptible to thermal aging at light water reactor coolant temperatures. Effects of thermal aging on tensile strength, hardness, and other mechanical properties have been reported, but the effect of thermal aging on the stress corrosion cracking (SCC) growth rate in SUS630 under BWR conditions has not been reported. In this study, SCC growth tests were performed on unaged and thermally aged SUS630 in a simulated BWR environment to investigate the effect of thermal aging, stress intensity factor, and hardness on SCC growth rates. From these results, we propose an equation for the SCC growth rate in SUS630.