Radiation hardening and IASCC susceptibility of extra high purity austenitic stainless steel

An extra high purity austenitic stainless steel (EHP alloy: Fe–25Cr–35Ni SAR) was developed with countermeasures for irradiation assisted stress corrosion cracking (IASCC). To study the radiation-induced hardening and the susceptibility of IASCC for EHP alloy, EHP alloys were irradiated at 553±20K in a helium and nitrogen gas mixture at the fluence level of 1.5×1025n/m2. After neutron irradiation, tensile tests and slow strain rate tests (SSRTs) of irradiated specimens were conducted in air at 561K and in oxygenated high purity water at 561K, respectively. The fracture surfaces were examined using SEM after tensile tests and SSRTs. The tendency of radiation-induced hardening of EHP alloy was the same as irradiated type 304 and type 316 stainless steels. Though there was a little effect of the countermeasures on the suppression of irradiation hardening. EHP alloy had excellent resistance for IASCC up to 1.5×1025n/m2.