Study on high temperature low cycle fatigue behavior of P92 steel under 630℃

P92 steel has been widely applied in high temperature components of power plants. With the development of the ultra supercritical power plants, the operating temperature of P92 steel has been promoted. The high temperature fatigue performance of P92 steel has a significant effect on the safety of power plants. Therefore, the fatigue test of P92 steel under 630℃ was conducted, and the effects of the strain amplitude and strain rate on the fatigue life was studied. In addition, the fatigue fracture mechanism for P92 steel was investigated by the fracture morphology analysis. The results indicated that P92 steel exhibited a cyclic softening behavior at high temperatures. The fatigue life decreased exponentially with the increasing of plastic strain amplitude. In contrast, the improvement of strain rate would promote the fatigue life. Furthermore, the fatigue fracture surface of P92 steel consisted of three zones, including fatigue source region, fatigue crack growth zone and fracture zone. The decrease of fatigue life at high strain amplitude was mainly induced by the increase of creep cavities and secondary cracks.