MCrAlY coating design based on oxidation-diffusion modelling. Part I: Microstructural evolution

To improve the efficiency of modern gas turbines, it is highly desired to develop durable MCrAlY alloys, to be used as protective coatings against oxidation and corrosion for superalloys which are the base materials for some hot components like turbine blades and vanes. In this paper, an oxidation-diffusion model was used to simulate the diffusion of alloying elements and the corresponding microstructural changes in different superalloy-coating systems at high temperature. Two important processes are considered in this model: oxidation of the coating and interdiffusion between the superalloy and the coating. The model showed an accurate predictability of the diffusion and microstructural evolution in real superalloy-coating diffusion couples studied at high-temperature exposure. The model was further applied to investigate the elemental effects of Ni, Co, Cr and Al on the microstructural evolution, considering the development of two important phases in superalloys and coatings, i.e. FCC-γ′ and BCC-β, at different temperatures. The results in this paper deepen the knowledge of the MCrAlY coating design for superalloy-coating systems in high-temperature applications.