In situ SCC observation on neutron irradiated thermally-sensitized austenitic stainless steel

To examine the crack initiation and growth of irradiation assisted stress corrosion cracking (IASCC), in situ observations of the specimen surface were conducted during slow strain rate testing (SSRT) in oxygenated high purity water at 561 K. Each specimen of type 304 stainless steel was treated by solution annealing (SA), thermal sensitization (TS) or cold working (CW). After neutron irradiation of 1.0 × 1026 n/m2 (E > 1 MeV), the gage length section of specimen was observed through a window equipped in the autoclave of SSRT machine and images were recorded automatically at regular intervals. Crack initiation was observed immediately after the maximum stress during SSRT of each specimen. The ranking of mean crack growth rate based on the images was CW > TS > SA. The relative susceptibility to IASCC estimated by fraction of intergranular stress cracking on fracture surface was observe to be SA > TS > CW.