IASCC susceptibility and slow tensile properties of highly-irradiated 316 stainless steels

Irradiation assisted stress corrosion cracking (IASCC) of cold-worked 316 stainless steels irradiated to doses up to 53 dpa was examined using slow strain rate tensile tests in 593 K simulated pressurized water reactor primary water while changing the content of dissolved hydrogen (DH) and dissolved oxygen (DO). A higher susceptibility was observed for higher doses and DH content, accompanied by increased corrosion product formation on the fracture surface and higher hydrogen accumulation near the fracture surface. At 53 dpa the susceptibility at both 0.02 and 8 ppm DO was comparable to that at high DH content. The results indicated that IASCC was sensitive to DH content at doses less 14 than 35 dpa but was less sensitive to both DH and DO content at 53 dpa. The subcrack formation and hydrogen accumulation in the hydrogenated condition suggested that processes associated with hydrogen would have an important role in IASCC in hydrogenated water. The same stainless steels were susceptible to intergranular type fracture during 14 slow tensile tests in pure argon at 593 K. The intergranular type region consisted of a mixture of intergranular and dimple regions, and the intergranular fraction was much smaller than that in IASCC in water environment.