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 ± 20 K in a helium and nitrogen gas mixture at the fluence level of 1.5 × 1025 n/m2. After neutron irradiation, tensile tests and slow strain rate tests (SSRTs) of irradiated specimens were conducted in air at 561 K and in oxygenated high purity water at 561 K, 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 × 1025 n/m2.