Stress Corrosion Cracking Initiation Behavior of XM-19 Stainless Steel Under Long-Term Uniaxial Constant Load Testing in High-Temperature Water Available to Purchase

XM-19 stainless steel (ASME SA479; UNS S20910) was used as a structure material of a light water reactor as an alternative material of Type 304 (UNS S30400) stainless steel. XM-19 stainless steel is an attractive alternate to Type 304 stainless steel for these applications and was developed specifically as a high-strength corrosion-resistant replacement for Type 316 (UNS S31600) stainless steel. Although stress corrosion cracking (SCC) resistance was fundamentally excellent, there was little examination of the influence of applied stress of the long-term SCC resistance in the high-temperature pure water. To evaluate its fitness as a nuclear reactor structure material, SCC testing by uniaxial constant load in high-temperature pure water, 288°C (dissolved oxygen [DO]: 8 ppm) was carried out. SCC was observed above 1.35σy. Below 1.33σy, no SCC failure occurred, but small cracks were observed above 1.0σy. These results suggest that an applied stress near the yield strength can produce susceptibility to SCC.