Research on creep-fatigue lifetime of GH4133B superalloy at elevated temperature used in turbine disk of aero-engine

Abstract

At high temperature of 650°C, the creep-fatigue lifetime tests for sheet specimens of GH4133B superalloy used in turbine disk of an aero-engine are conducted in two types of loading to study the creep-fatigue behaviour and to investigate the effect of loading parameters on fatigue lifetime. The results show that the creep displacement curve consists of three stages as initial creep, stable creep and accelerated creep, and the creep-fatigue interaction accelerates the accumulated fatigue damage, which leads to reducing fatigue lifetime. Under the condition of different stress ratios at a fixed maximum stress 700 MPa, the creep-fatigue lifetime firstly decreases, and then increases with increasing stress ratio, there is a minimum creep-fatigue lifetime when the stress ratio is of 0.1. The creep-fatigue tests at various maximum stress levels show that there exists a mean stress threshold value about 330 MPa for the superalloy, as the mean stress is above 330 MPa, the influence of creep deformation on creep-fatigue damage is remarkable, resulting in the dramatic reduction of creep-fatigue lifetime.