Ion irradiation-induced microstructural changes in heat-affected zone of stainless weld overlay cladding of RPV steel

Ha, Yoosung  ; Takamizawa, Hisashi ; Hanawa, Satoshi ; Nishiyama, Yutaka ; Ebisawa, Naoki*; Toyama, Takeshi*; Nagai, Yasuyoshi*

Heat affected zone (HAZ) under stainless overlay cladding of RPV steel was irradiated by iron ions. To investigate the mechanism of irradiation hardening, the solute clusters distributions were confirmed by 3D-Atom Probe Tomography analysis, and the correlation between the irradiation hardening and the microstructure change in HAZ and matrix was discussed. As result of APT analysis, Cu and Si-Mn-Ni clusters were observed in irradiated area, but not in un-irradiated area. The distributions of cluster were different in coarse grain HAZ, fine grain HAZ and matrix, and the amounts of clusters in matrix were significantly lower than that in HAZ. In addition, size, chemical composition and number densities of clusters and their distributions were correlated with irradiation hardening.