Effect of heat treatment on Coffin–Manson relationship in LCF of superalloy IN718

Low cycle fatigue (LCF) behavior of the Ni–Fe-based superalloy IN718 was examined in various heat-treated conditions. The alloy was subjected to solution treatment, peak ageing, over ageing and extra over ageing to study the role of precipitates on its LCF behavior. This alloy is found to exhibit dual slope Coffin–Manson relationship in all the above heat-treated conditions examined. While the slope of the segment corresponding to the region of high strain is lower than that of the region of low strain amplitude for solution treated, peak aged and extra overaged conditions, there is reverse trend in the slope of the two segments in the overaged condition.