Abstract
In recent years, in order to estimate the residual life assessment of thermal power plants, creep damage evaluation method in heat affected zone (HAZ) has become more important. In this study, we aimed at elucidation of the three-dimensional microstructure of 9Cr-1Mo steel which is often used in high temperature conditions. We observed the three-dimensional geometry of fine grained HAZ using the "3D-EBSD method", and made the quantitative evaluation. It is suggested that both creep voids and grain are coarsening as damage progresses and this growth is occurring rapidly in the late stage of damage. In addition, according to the three-dimensional distribution, voids are often lined up in parallel to the direction of stress, and are present scattered around. Therefore considering the previous studies (1Cr-1Mo) that grain size does not change and voids are lined up like a crack along the grain boundaries perpendicular to the direction of stress, this growth model of creep voids in the fine grained HAZ of 9Cr-1Mo steel is significantly different from previous studies.
