Abstract: Fatigue is the main reason for fracture of structure. The fatigue damage and fracture mechanism of GH4133B superalloy used in turbine disk of aero-engine are studied. The fatigue limit of GH4133B is measured, and the relation between the ratio of resistance change and the fatigue cycle is investigated at room temperature. The experiment data are processed by using the regression analysis and the probabilistic method, the theoretical fatigue threshold and P-S-N representation are achieved, and the fatigue damage evolution equation is deduced. The results show that the theoretical fatigue threshold agrees well with the experimental one, and the modified Chaboche model can precisely predict the accumulated damage of GH4133B. Then, the fracture surfaces of GH4133B are micro analyzed by using scanning electron microscopy(SEM). It can be found from the fracture surface morphologies that in the initiation region, the superalloy exhibits a mixed fracture mode and many secondary cracks emerge. In the propagation region, a series of typical fatigue striations can be observed, especially at lower stress amplitude, some brittle fatigue striations can be found. In the final rupture region, the fracture surface appears as a typical semi-brittle fracture mode, furthermore, the size and number of dimples decrease with the increase of stress amplitude.

Key words: Damage, Fatigue, Fratrography, Turbine disk