The effect of thickness on the creep response of thin-wall single crystal components

An understanding of the micromechanics of high temperature creep and damage accumulation in single crystal nickel base superalloys is important for the design of turbine blades and vanes in advanced commercial and military gas turbines. Advanced turbine blades are typically thin-walled cooled structures made of single crystal nickel base superalloys. Testing has shown that the creep response is larger in these thin wall structures than in test specimens typically used to characterize the material. It has also been experimentally observed that creep rupture lives obtained at moderate to high temperatures decreased sharply (∼60%) with a reduction in specimen thickness by approximately eight times. We have developed a dislocation-based model to help explain this effect. The model considers the interaction of dislocations with the surface and the effect of nucleated intrusions or/and extrusions on creep strain rate.