Abstract: Fatigue life is composed of crack initiation life and growth life. The fatigue crack propagation tests of GH4133B superalloy used in turbine disk of aero-engine are carried out under different stress ratios at room temperature, and the fatigue crack growth threshold values are measured. It is shown from the regression analysis by Paris formula that the crack growth rate increases with increasing stress intensity factor and stress ratio, and the modified Paris formula considering threshold value can describe the fatigue crack growth behavior accurately. The crack growth path is observed by an optical microscopy, and the fracture surface morphologies are investigated using scanning electron microscope. It is shown that with increasing stress intensity factor, the crack growth path changes from a straight line to a tortuous trail. In the crack initiation, steady growth and rapid growth region, the fracture surface individually exhibits a cleavage fracture mode, a series of fatigue striations and a mixed intergranular dimple fracture mode. Finally, the crack growth equations and loads are derived using the inverse educing method. It is suggested that the inverse equations can predict the crack growth behavior, and the predict results can effectively prevent the occurrence of fatigue fracture.

Key words: Crack propagation, Fatigue, Fratrography, Stress ratio, Turbine disk