Remaining creep properties and fracture behaviour of P92 steel welded joint under prior low cycle fatigue loading

The alternation of creep properties is unavoidable in welded structures after suffering from cyclic damage, which may lead to the premature failure of power plant units and hard to predict. This work is devoted to clarify the influence of prior low cycle fatigue (LCF) loading on subsequent creep properties and fracture behaviour of P92 steel welded joint. Prior LCF tests ranging from 0%N_f to 70%N_f and subsequent creep tests were performed at 650 °C. Results indicate that the remaining creep life of P92 steel welded joint is significantly reduced by prior LCF loading, whereas the creep ductility has a pronounced increase. Importantly, the reduction of remaining creep life of welded joint is greater than that of homogeneous base metal, while the creep rupture strains of welded joint and base metal show opposite evolution. Fractography of failed specimens reveals that the creep fracture location depends on prior LCF damage. Additionally, the remaining creep properties were evaluated with a proposed fatigue damage parameter, and the sensitive regions of fatigue damage on remaining creep properties were determined.