Creep life estimation of a service-exposed P91 cross-weld joint based on a primary-secondary creep deformation model

Creep deformation and rupture behavior of welded joints from service-exposed P91 steel were investigated by creep tests and microstructure examination. A series of miniature tensile creep tests were conducted at 569 degrees C under applied stresses ranging from 182.5 to 286 MPa for the heat-affected zone (HAZ), base metal, and weld metal. Creep deformation behavior was modeled using the experimentally measured creep strain data as the primary creep-secondary creep (PC-SC) model and fitting closely with the measured creep curves of each metal. Power-law type creep equations were employed to describe the primary and secondary creep behavior. The creep rupture life of the cross-weld specimen was predicted using the PC-SC model with HAZ properties. An accurate prediction was possible if the stress in estimation was increased to 1.14 times of the actual applied stress. The creep test results with the cross-weld specimens were used for verification. Applying the Monkman-Grant relationship and the creep damage tolerance factors to the cross-weld joint life prediction are also discussed.

Automated summary

In this study, the creep deformation and rupture behavior of welded joints from service-exposed P91 steel were investigated. The experimentally measured creep strain data were used to model the creep deformation behavior and predict the creep rupture life of the cross-weld specimen. Factors such as stress estimation and creep damage tolerance were discussed for life prediction of cross-weld joints.