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(Le 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.