The effect of hardening source in proton irradiation-assisted stress corrosion cracking of cold worked type 304 stainless steel

The goal of this study is to discern whether the irradiation-assisted stress corrosion cracking (IASCC) susceptibility depends on the source of hardening rather than hardening alone. A set of five hardened conditions of commercial 304SS were studied in which the level of hardening remained fixed while the contributions from irradiation and cold work (CW) varied. The extremes of this set were hardening by either proton irradiation at 1.67 dpa only or 35% cold work only. Between these extremes the same value of hardness was reached with a combination of cold work and irradiation. Cold work/proton irradiation combinations used to achieve the target level of hardness were 10% CW + 0.55 dpa, 20% CW + 0.25 dpa, and 25% CW + 0.09 dpa. Proton irradiation was conducted with 3.2 MeV protons at 360°C at a rate of 7 × 10 ^-6 dpa/s. The specimens were then subjected to stress corrosion cracking (SCC) tests in 288°C water typical of normal water chemistry in boiling water reactor (BWR) service conditions. Only the 0% CW + 1.67 dpa and the-10% CW + 0.55 dpa samples showed any sign of IASCC as manifested by intergranular (IG) cracking despite all of the specimens being at the same hardness. All other samples failed without any evidence of IG cracking. Results from this study suggest that radiation hardening, in contrast to cold work, has the most pronounced effect on IASCC.