表面硬化層を有するオーステナイト系ステンレス鋼の 高温水中SCC感受性評価
概要
The core shroud specimens (316L stainless steel) were used to characterize the surface hardening layer introduced by machining and to evaluate the SCC susceptibility in the simulated BWR coolant environment. Based on the results obtained, the effect of the surface hardening layer on the SCC susceptibility and its mechanism are discussed. It is suggested that the wall part has clearly higher SCC susceptibility than the support ring part when compared between the as-received materials (with surface hardening layer). The reason for this is that in the specimens used in this study, the effect of machining was considered to be more significant in the wall from the observation of the microstructure after etching and the measurement of the hardness distribution in the surface layer. On the other hand, when the specimens without hardened layer and with colloidal silica finish were compared with each other, a few micrometers deep cracks were observed in both specimens, and the difference in SCC susceptibility was not clear.
