Stress Rupture Behavior of Modeling Specimen with Cooling Holes of Single Crystal Superalloy DD6

Experimental and finite element study on the stress rupture behavior of single crystal superalloy DD6 has been performed with modeling specimens with and without cooling holes at 980℃/300 MPa. The results indicate that the stress rupture life of specimens with cooling holes is 69 h, lower than that without cooling holes(90 h) at the same nominal stress conditions. The stress concentration around the cooling holes is the major factor. Scanning electron microscopy analysis on the fracture surface reveals that the specimens without cooling holes fractured in the mode of microvoid coalescence and the fracture surface was made up of small square-shaped facets. As for the specimens with cooling holes, the cracks propagated fast near the holes. Based on the crystal plasticity theory, a creep model was established, and used in the ABAQUS user subroutine (UMAT) to simulate the plate specimens with and without holes. The results show that the fracture position and fracture pattern are consistent well with finite element numerical analysis. In engineering, the creep model can be used to predict the stress rupture life of thin-walled plate specimens.