The effects of prior creep–fatigue on the strain rate sensitivity of a P92 welded joint

The high-temperature creep–fatigue (CF) interaction on the service damage of P92 welded joint was uncovered based on the evolution of local strain rate sensitivity of strength by nanoindentation. The individual creep, fatigue and creep–fatigue loadings were performed to reveal the CF interaction on both the structure and mechanical properties of the welded joint. And CF loadings interrupted at lifetime fractions of 10%, 20%, 30%, 60%, 100% were adopted to acquire the high-temperature service damage evolution. The structure changes of the heterogeneous welded joint during service damage were characterized by using electron backscatter diffraction method. According to structure evolution including the changes of grain size and dislocation density during high-temperature deformation, we systematically discussed the local variation mechanism of hardness and SRS at different microstructural zones.