The effects of tensile and compressive dwells on creep-fatigue behavior and fracture mechanism in welded joint of P92 steel

Highlights: • Longer CF life under tensile dwell in comparison to compressive dwell. • Different local creep behaviors were observed for the two dwell modes. • The hardness, elastic modulus and creep resistances near fracture edges were clearly reduced. • Two independent fracture mechanisms were suggested for tensile and compressive dwells. The creep-fatigue interactions on the long-term service damage of P92 welded joint were investigated on the tensile and compressive holdings with a series of applied strains, respectively. The local mechanical properties including hardness, elastic modulus and creep resistance of welded joint were uncovered using nanoindentation. The features of fracture morphology and internal defects after CF tests were studied by scanning electron microscope. Based on the characteristic of microstructural evolution and the variation in local mechanical properties, holding type effects of creep-fatigue interaction on the local creep behavior and fracture mechanism of the welds were systematically investigated.