Fatigue–creep behavior of 1.25Cr0.5Mo steel at high temperature and its life prediction

High-temperature stress controlled tests for 1.25Cr0.5Mo steel were carried out at different loading conditions to investigate the fatigue–creep interaction behavior. Four fatigue–creep facture character maps have been established. It is found when the stress amplitude is less than the mean stress after a sort, drastic interactions between fatigue and creep will occur, the fracture life will decrease rapidly and the fracture ductility will reach its minimum. As the complex relationships between fracture life and its influencing factors can be well explained by the mean strain rate at half-life, which is considered as the main factor associated with the fracture life. Moreover, based on the ductility exhaustion theory and the effective stress concept, a new model for fatigue–creep life prediction under stress control is proposed. Most of the test data are predicted within a factor of ±×1.5, which is better than the frequency separation method (FS) and the strain energy frequency modified approach (SEFS).