Thermal fatigue of coated superalloys

Abstract

The penetration of a coating crack into the base metal has been analyzed with the aid of a fracture mechanics model. Differential thermal expansion between the coating and substrate, together with coating thickness and the coating-substrate elastic modulus ratio are shown to significantly affect the rate of crack propagation into the substrate. From a thermal fatigue standpoint, the results obtained using this model indicate that a significant incentive exists to develop coatings which are thin and provide small compressive thermal expansion mismatch strains in the coating on cooling.