The Clarification of the Occurrence Mechanism of Creep Micro Cracking at Weld Joint based on Vacancy Diffusion Analysis

Abstract

Since high temperature creep condition was applied to thermal power plant components for long-term, it is important to evaluate the creep fracture life. Especially, the reduction of the creep strength at weld joint induced by micro creep cracking is important problem. Though there are many researches which concern the creep crack growth and the creep damage formation for weld joint, the mechanism of creep damage formation has not yet been clarified. The creep void initiation and growth under high temperature creep condition is considered to be caused by vacancy diffusion and concentration. Therefore, it is important to clarify the vacancy diffusion and concentration behavior. However, it is difficult to observe the vacancy diffusion behavior in experiment. Therefore, numerical analysis is the most effective technique to evaluate the vacancy diffusion behavior. In this study, relationship between the site of stress concentration and the vacancy diffusion behavior at weld joint was analyzed using proposed two-dimensional stress induced vacancy diffusion analysis. And it was related to crack initiation at the weld joint.