Research on Fatigue Crack Initiation and Short Crack Propagation of GH4133B Superalloy Used in Turbine Disk of Aero-engine

Fatigue crack initiation and short crack propagation is the key and foundation of damage tolerance design of aero-engine components. The researches on fatigue crack initiation and short crack propagation under different notch radii and stress ratios for GH4133B superalloy used in turbine disk of aero-engine are carried out at ambient temperature. It is shown that a control parameter Delta K(I)/(r( rho ))(0.5) can be used to characterize the fatigue crack initiation life, and the effect of notch radius on fatigue crack initiation life increases with increasing control parameter, while the fatigue crack initiation life firstly increases and then decreases with increasing stress ratio. An effective stress intensity factor range Delta (Keff), can be adopted to describe the deceleration and acceleration of crack growth rate during the short crack propagation. The fatigue fracture surface morphologies are investigated using scanning electron microscopy. It is shown that there is a cleavage step between two adjacent radial stripes, and a series of early fatigue striations exist on the cleavage step, which reveals the microscopic mechanism of short crack propagation from the point of view of fracture surface morphology that the fatigue crack growth rate is intially higher, and then gradually decreases with the propagation of short crack.