Creep behavior of thin-walled plate with cooling holes of nickel-based single crystal superalloy DD6 under high temperature

Thin-walled plate specimens with cooling holes were used to model the air-cooled turbine blades. Specimens without holes were employed for comparison. The effect of cooling holes on the creep life of nickel-based single crystal cooling blades was studied. Experimental results show that at 950°C, the creep lives of specimens without cooling holes are nearly twice the specimens with cooling holes when the stress is kept as 377 MPa. The scanning electron microscopy(SEM) analysis on the fractured surface reveals that the creep damage stems from the local region around the holes and the ruptures initially occurs at holes edges. Based on the crystal plasticity theory, a creep model for the creep experimental data of single crystal material was developed, and implemented into the Abaqus user subroutine(UMAT) to simulate the plate specimens with and without holes. The results show that stress concentration and redistribution occur around the cooling holes, and the form of the fracture surface is consistent well with numerical analysis. For engineering application, the relationship between the creep life and the maximum resolved shear stress amplitude of dodecahedron slip system is expressed by an exponential function. The creep test result shows that the formula has good accuracy under 950°C, 377 MPa.