Stress corrosion cracking (SCC) near the welded zone of core internals and recirculation piping of Type 316L stainless steel in BWR nuclear power plants has been observed at the surface where tensile residual stress exists due to welding and/or surface-machining. It is well-known that butt-welding of austenitic piping causes the tensile stress in the inner surface of the pipe and that surface-machining is usually conducted before and after piping butt-welding to match the internal diameter (ID) of pipes and to provide a smooth surface finish but some amount of hardening. The SCCs near the welds of Ni-based alloys have been observed in the environment of primary water coolant, which is so called PWSCC. In this case, both residual stress and hardening are also the most important factors induced by welding as well as surface-machining in the regions of interest. In this work, therefore, Vickers hardness and residual stress distributions at work hardened layer such as inner surface of piping butt-weld by surface-machining before and after welding were experimentally evaluated. A simulation using a local micron-scale finite element method (FEM) model has been performed to support the understanding of experimental data by a model which was proposed in previous paper (PVP2006 and 2008 [1, 2]). Redistribution behavior of residual stress by welding after surface-machining will be discussed based on experimental and analytical results with regard to crack growth behavior.

This content is only available via PDF.
You do not currently have access to this content.