Micromechanics of failure of aluminide coated single crystal Ni superalloy under thermomechanical fatigue

Abstract

Ni-base single crystal superalloy turbine components show better creep resistance than their polycrystal counterparts and are used as blades and vanes in aircraft and gas turbine engines. In order to achieve higher operating temperatures combined with good environmental performance, a range of coatings and intermediate coatings are being examined. In this respect it has been realized that the thermomechanical fatigue (TMF) response is a major life limiting factor. The aim of this paper is to determine the influence of an aluminide coating on the TMF lives of a CMSX4 single crystal superalloy and to identify the dominant failure mechanism operating under out-of-phase TMF testing conditions. 300--1,050 C, 135{degree} out-of-phase mechanical loading cycles have been chosen to represent the harshest conditions faced at a critical location across on a blade in service. This information is of great significance to aero-space industries and provides a sound basis for predicting the TMF lives of superalloy components.