Analysis of deformation behavior at SCC crack tip, 3; Plastic deformation analysis by EBSP method

Kaji, Yoshiyuki  ; Miwa, Yukio; Tsukada, Takashi ; Nagashima, Nobuo*; Hayakawa, Masao*; Ando, Masami*; Nakata, Kiyotomo*; Koshiishi, Masato*

In recent years, incidents of the stress corrosion cracking (SCC) were frequently reported that occurred in the weld part of core shroud and primary loop recirculation (PLR) piping of low carbon stainless steels, and the cause investigation and measure become the present important issue. In this study, to investigate the effect of plastic deformation behavior at the crack, analyses of plastic deformation behavior at the SCC crack tip were performed by electron back-scattering diffraction pattern (EBSP) method. SCC crack propagated along the grain boundary in the 45 degree direction of a fatigue crack, especially random grain boundary. The plastic deformation showed 10 to 20% in the one grain region of the crack. The plastic deformation behavior was different in both of a SCC crack and large plastic deformation was observed on one side of grain. From these results, it was considered that SCC crack propagation behavior was controlled by plastic deformation of very near crack tip.