Microstructure development of an electroplating coated nickel based SC superalloy in oxidation processes: simulation results

This paper is the second part of our serial study, by focusing on simulation. An oxidation-diffusion kinetic model was applied to simulate the microstructure development in a MCrAlY-superalloy system in oxidation process. The interdiffusion behavior of elements in various MCrAlY-superalloy systems was also simulated by changing the composition of MCrAlY coatings. With the help of the modelling, the mechanism of the formation of the diffusion zones in the single crystal (SC) superalloy can be better analyzed. The results clearly revealed that the inward diffusion of Al from coating affected the depth of secondary reaction zone (SRZ) with the precipitation of TCP phases while the depth of interdiffusion zone (IDZ) was decided by the inward diffusion of Cr and Co. The influence of the internal oxidation on the microstructure development of the coating and superalloy was also discussed with some thermodynamic calculations.