Effect of Weld Overlay Repair on Residual Stress and Crack Propagation in a Welding Pipe

Abstract

Intergranular stress corrosion cracking (IGSCC) has been still one of concerns at the weld zone in boiling water reactors (BWRs). Therefore, Weld Overlay (WOL) process has been developed and applied to repair of BWR pipe joints. To understand residual stress and crack growth behavior is important to evaluate the reliability of pipe joints with WOL. In this paper, the residual stresses were calculated by using thermal elasto-plastic analysis by finite element method (FEM). The analytical model was assumed the primary loop recirculation (PLR) pipe joint with WOL followed by the Japanese guideline. The tensile hoop residual stress was changed to compressive stress on the inner surface of the pipe. On the other hand, tensile axial residual stress was occurred on the inner surface of the pipe by butt-welding and some WOL cases increased the tensile axial stress. In addition, the stress intensity factor for fully circumferential cracks was evaluated using calculated residual stress distributions. As a result, the effect of application of WOL on the crack growth behavior is insignificant in PLR pipe joint.