Effect of Long-Term Thermal Aging on SCC Initiation Susceptibility in Low Carbon Austenitic Stainless Steels

The objective of this study was to clarify the effect of long-term thermal aging on SCC initiation susceptibility in low carbon austenitic stainless steels. Specimens used were Type 304L and 316L austenitic stainless steels. Both steels were cold worked to 20% thickness reduction (CW) followed by long-term thermal aging at 288 °C for 14,000 h (LTA). Creviced Bent Beam (CBB) testing was carried out to estimate the SCC initiation susceptibility under BWR simulated water condition at high temperature. The results of the CBB tests showed that Type 304L specimens with CW and LTA treatment exhibited no SCC susceptibility. In contrast, the SCC initiation susceptibility of Type 316L increased by the combination of cold work and long-term thermal aging. To understand these results, evaluations on the changes of microchemistry, microstructure and mechanical properties induced by the CW and LTA treatment have been performed, and their correlation with the SCC initiation susceptibility was discussed.