Effects of Heat-Treatment Residual Stress on Low Cycle Fatigue Life of a Turbine Disk in PM Superalloy

Abstract

Turbine disks in powder metallurgy (PM) superalloy have been widely used in advanced aeroengines. The production of PM superalloy turbine disks involves a series of heat treatment processes, which would inevitably create residual stresses. It has been proved that the low cycle fatigue (LCF) life of the turbine disk is affected by the residual stresses. The computational simulation of heat treatment is considered as an effective way to evaluate the residual stresses in a turbine disk. A finite element software was used to simulate the heat-treatment processes of a FGH95 turbine disk to obtain the residual stress field. To investigate the relaxation of residual stress in FGH95, smooth bar specimens were measured by X-ray diffraction before and after being loaded. Modified by the residual stresses, SWT model is used to predict the low cycle fatigue life of the turbine disk modified by the residual stress field obtained from the simulation of heat treatment. By the comparison between the prediction modified by the residual stress and the prediction without modification, a considerable decrease in low cycle fatigue life is indicated.