The Influence of Dwell Time on Low Cycle Fatigue Behavior of Ni-base Superalloy IC10

Low cycle fatigue and creep-fatigue experiments of IC10 Ni-base superalloy plate specimens with multiple holes were performed below 1,000 °C. The average fatigue life is 10^5.4 cycles, while the creep-fatigue life is 10^3.4 cycles, which shows that the life of creep-fatigue is reduced 1-2 times compared with low cycle fatigue life. After tests, the detailed fracture and microscopic structure evolution were observed by scanning electron microscopy (SEM); meanwhile, the constitutive model based on crystal plasticity theory was established and the fracture mechanism was analyzed. Three conclusions have been obtained: First, the load during dwell time leads to the damage accumulation caused by deformation and the interaction of fatigue and creep shortens the service life of materials seriously. Second, in order to maintain the macroscopic deformation, a new slip plane starts to makes the dislocation slide in reverse direction, which leads to fatigue damage and initial cracks. Third, the inner free surface creates opportunities for escape of the dislocation line, which is caused by the cavity. What's more, the cure dislocation generated by cyclic loading contributes to the formation and growth of cavities.