Low-cycle Fatigue Life of DD3 Single Crystal Nickel-based Superalloy

Low cycle fatigue experiments of single crystal superalloy DD3 in the 001,011 and 111 orientations under asymmetrical cyclic loading at 680℃ were performed.The crystallographic orientation affected low cycle fatigue life of DD3 single crystal superalloy significantly,the life in the 001 orientation was the longest and the life in the 111 orientation was the shortest.By modifying strain range with an orientation function,the effect of crystallographic orientation on fatigue life could almost be eliminated.A variable k was introduced to describe the effect of the mean stress from asymmetrical cyclic loading on the fatigue life.The relationship between cyclic life and k indicated a power law.By using total strain range,crystallographic orientation function and the variable k as failure parameters to fit the low cycle fatigue tests data of smooth specimens or notched specimens,the correlation coefficient would be the largest with multivariate linear regression analysis under both uniaxial stress state and complex stress state.