Effect of Environment and Prestrain on IASCC of Austenitic Stainless Steels

摘要

The effect of environment and prestrain on IASCC of austenitic stainless steels was investigated in post-irradiation CERT tests in Ar at 288°C and simulated BWR NWC. Two alloys susceptible to IASCC were selected for this study, which are commercial alloy 304 and high purity Fe-15Crl2Ni. Samples were irradiated to 5 dpa with 2 MeV protons at 360°C and strained to about 2% in Ar at 288°C. The results showed that the water environment is the key to inducing IASCC at 288°C. No intergranular cracking was observed in either alloy following straining in Ar up to ~3.5%. However, cracking occurred once the samples were subsequently strained to an additional 1% in simulated BWR NWC. Cracks tended to be long and extend over many grain boundaries rather than single grain facets, perhaps due to the prestrain in Ar. Cracking induced by 0.2% plastic strain in simulated BWR NWC in CP304 with 3.4% prestrain in Ar was also observed. Normal stress is critical in determining the crack initiation location in CP304 and Fe-15Cr12Ni when strained in simulated BWR NWC because the cracked grain boundaries were preferentially aligned perpendicular to the tensile direction.