Creep damage evolution in a modeling specimen of nickel-based single crystal superalloys air-cooled blades

Plate specimens both with holes and without holes were used to model air-cooled turbine blades. Experimental study on the creep behavior of a second generation nickel-based single crystal has been performed at 980 deg. C with these modeling specimens in two crystallographic orientations [0 0 1] and [1 1 1]. The results of creep tests show that crystallographic orientations and cooling holes have remarkable influence on the stress rupture behavior. The scanning electron microscopy (SEM) observation on the fractured surface shows that the cavitation-controlled damage is the main mechanism inducing fracture. So the finite element analysis (FEA) with a modified form of Kachanov-Rabotnov damage law was carried out to simulate the damage evolution in modeling specimen with cooling holes in crystallographic orientation [0 0 1]. The FEM results reveal that the existence of cooling holes causes the stress and strain concentrations near the holes. The creep damage is localized in the cooling holes region, where the fracture will happen easily. The numerical result is coincident with the fracture appearance of the specimen