Analysis of Type IV Creep Failure for P91 Steel Welded Joint Based on Thermal Displacement of Steam Pipeline

Abstract

AbstractType IV creep failures tend to occur on fine grained heat affected zone (FGHAZ) of P91 steel welded joint after long-term service at high temperature. In this paper, simulation of finite element is applied to analyze the stress response of the component. Experimental result of stress obtained from real-time monitoring is conducted to verify the simulation. The research results show that the concentration of maximum principal stress is caused by thermal displacement of the piping system. The microstructure of the welded joint is studied by SEM and EDS and the area in which maximum principal stress concentrates is in good agreement with distribution of creep cavity, that is the characteristic of Type IV creep failure in earlier stage. The value of maximum principal stress is improved and the distribution is changed, which are sensitive to thermal displacement cooperation. So thermal displacement that results in accumulation of creep cavity and Type IV cracking is regarded as remarkable factor.