Crack Growth Behaviour of P92 Steel Under Creep-fatigue Interaction Conditions

Abstract

Creep-fatigue interaction tests of P92 steel at 630℃ under stress-controlled were carried out, and the crack propagation behaviour of P92 steel was studied. The fracture mechanism of crack growth under creep-fatigue interaction and the transition points in a-N curves were analyzed based on the fracture morphology. The results show that the fracture of P92 steel under creep-fatigue interaction is creep ductile fracture and the (Ct)avg parameter is employed to demonstrate the crack growth behaviour; in addition, the fracture morphology shows that the crack growth for P92 steel under creep-fatigue interaction is mainly caused by the nucleation and growth of the creep voids and micro-cracks. Furthermore, the transition point of a-lg(Ni/Nf) curve corresponds to the turning point of initial crack growth changed into steady crack growth while the transition point of (da/dN)-N curve exhibits the turning point of steady creep crack growth changed into the accelerated crack growth.

Keywords

• P92 steel
• creep-fatigue interaction
• crack growth
• fracture morphology
• fracture parameter