Prediction of long-term creep-fatigue life of stainless steel weldment based on microstructure degradation

This paper describes a newly developed analytical method for the evaluation of creep-fatigue strength for stainless weld metal. Based on the observation that creep-fatigue crack initiated adjacent to the interface of sigma-phase/delta-ferrite and matrix, a mechanical model, which allowed the evaluation of micro stress/strain concentration adjacent to the interface, was developed. Fatigue and creep damages were evaluated, using the model which described the microstructure after long time exposure to high temperatures. It is concluded that one major scope of this model is to predict analytically long term creep/fatigue life of stainless steel weld metals, the microstructure of which has been degraded as a result of in-service high temperature exposure.