Stress Corrosion Resistance of XM-19 Stainless Steel

XM-19 stainless steel (22Cr-13Ni-5Mn-2Mo-0.3N) is an attractive candidate for Boiling Water Reactor component applications where the thermal treatment during fabrication, coolant chemistry, and duty cycle loading combine to provide conditions too severe for more conventional stainless steels. The performance of the alloy was evaluated using the constant extension rate and pressurized tube test methods in 288 C (550 F) air saturated water, a more aggressive intergranular stress corrosion cracking (SCO environment than that encountered in-reactor. ASTM A262 Practice E sensitization tests were also used. Optimum processing parameters were determined by evaluating the effect of solution treatment temperature, the time/temperature sensitization and stress corrosion response plots, and the continuous cooling stress corrosion response plot. These data were used to select the optimum solution treatment temperature, the margin to sensitization during isothermal processing such as nitriding, and the quench rate required after solution heat treatment or stress relief to avoid sensitization. The effect of welding thermal treatments was also evaluated.