The effect of cyclic loading on the creep fatigue life and creep strength of a DS superalloy: Damage mechanism and life modeling

In this paper, the creep-fatigue behavior of directionally solidified superalloy DZ125 has been investigated by stress-controlled experiments at high temperatures with different dwell times. The endurance life(i.e Cumulated dwell time) has shown consistent changing trend with different load conditions. Crack growth form and creep-fatigue interaction are analyzed on the basis of microscope observation results. A new continuum damage mechanics(CDM) model is proposed and the damage behavior of DZ125 under different dwell times is systematically analyzed by this new model. Secondly, a life prediction model of high precision with fully coverage of dwell time and hold stress is proposed based on material's endurance strength decline and classical Larson-Miller life prediction method. Finally, the ultimate value of endurance strength decline of the superalloy affected by cyclic loads is determined for engineering application purpose.