Study on Construction Mechanism of Ceramic-Metal Thermal Barrier Coating System by Plasma Spraying

A unique construction mechanism is present in the plasma-spraying process of the ceramic-metal thermal barrier coating (TBC) system. This study combines experimental and simulation methods for investigating the mechanism of how three ceramic-metal TBC systems (Y2O3-MCrAlY, 8YSZ-MCrAlY, and Cr2O3-Ni20Cr) are constructed on Inconel718 alloy substrates. The three systems are bilayer coatings with a ceramic as the top coat (TC) and metal as the bond coat (BC). The coatings have different morphologies depending on the degree of softening, and substrate BC is more likely to achieve a higher metallurgical bond than TC-BC. The property differences between BC and TC may affect the bonding strength of the TBC systems. In constructing bilayer coatings, the temperature and equivalent stress of coating particles are related to their own thermal conductivity and thermal softening coefficient, respectively. In addition, constructing the TC is the main factor that causes the temperature effects, and constructing the BC is the main factor that causes the equivalent stress effects. Furthermore, the constructed BC first protects the substrate and reduces the influence of the TC that is later constructed on the substrate. This study provides a basic reference for relevant engineering applications and subsequent in-depth research on bilayer and multilayer coating systems.