SCC initiation susceptibility and corrosion behavior of grain boundaries of long-term thermal aged low carbon austenitic stainless steels in simulated BWR condition

Aoki, So  ; Kondo, Keietsu  ; Kaji, Yoshiyuki  ; Yamamoto, Masahiro 

The objective of this study was to clarify stress corrosion cracking (SCC) initiation susceptibility and corrosion behavior of grain boundaries of long-term thermal aged low carbon austenitic stainless steels in simulated BWR condition. Crevice Bent Beam (CBB) test was carried out to estimate the SCC initiation susceptibility under BWR simulated water condition. Surface and grain boundaries analysis of specimens was also carried out after the CBB test. The present results of the CBB tests showed that the SCC initiation susceptibility of Type 316L increased clearly by the combination of the cold work and the long-term thermal aging. Grain boundaries of Type 316L specimen which exhibited the SCC initiation susceptibility corroded with formation of Cr oxide, and the oxide formed along depth direction of grain boundaries. Based on these results, the correlation among SCC initiation susceptibility, SCC crack initiation and corroded grain boundaries will be discussed.