The effect of environment on the high temperature low cycle fatigue behaviour of cast nickel-base IN-738 alloy

Abstract

The high temperature low cycle fatigue behaviour of cast IN-738 nickel-base superalloy was studied at 850 °C. The effect of environmental damage on the low cycle fatigue life of this alloy was found to be significant with prior exposure at 1000 °C for 240 h in air. It was also found that the environmental damage caused the mode of crack initiation and propagation to change from the transgranular mode to the intergranular mode. The results were explained on the basis of the effect of the environment on the modes of crack initiation and propagation. Since different reductions in the fatigue life of this alloy were observed as a result of different thermal exposures, the effect of environment has to be accounted for in any high temperature low cycle fatigue lifetime prediction method.