Modelling of phase distributions in MCrAlY coatings and their interactions with nickel based alloys

Abstract
At high operating temperatures the oxidation resistant MCrAlY (M=Ni, Co) coatings and the substrate alloys are highly susceptible to phase changes, particularly, after long hours of exposure. With the advent of computational modelling involving metallurgical thermodynamics and diffusion parameters in recent times, it is now possible to follow these phase changes and interdiffusion processes through simulation. In the present work, phase changes in the temperature range between 950 and 1050 °C in the MCrAlY coating materials containing additions of Cobalt and Rhenium have been determined through such an approach. Further, using a diffusion simulation software interdiffusion between a commercial NiCoCrAlY coating and a Nickel-base superalloy substrate material at 1000 °C has been simulated. The simulated results have been compared with the experimental findings and they are found to be in reasonable agreement with each other. Some deviations observed are discussed in the light of limited availability of thermodynamic and kinetic data.