Fatigue behavior and life prediction model of a nickel-base superalloy under different strain conditions

The fatigue behavior of a nickel-base superalloy was investigated under total strain-controlled mode at high temperature. The fatigue life, cyclic stress response behavior and hysteresis loop of the superalloy were investigated under isothermal low cycle fatigue (LCF) conditions. The superalloy exhibited cyclic hardening and softening behaviors during the process of fatigue loading. The hysteresis loop shifted downwards slightly with the increase of the number of cycles. The fatigue life under different strain amplitudes reflects the interactions of dislocations and γ′ precipitates at elevated temperature. Three life prediction models to evaluate the fatigue life of the superalloy were evaluated for the LCF tests. The prediction values obtained by Manson-Coffin relationship agree well with the experimental results. The mechanisms of LCF were revealed through the observation of the microstructures by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The main deformation mechanism of the superalloy is the different interactions between dislocations and γ′ precipitates.