Structure evolution of multiscaled thermal barrier coatings during thermal exposure

Thermal barrier coatings (TBCs) are widely applied in protecting metallic components, which are used in aero- and land-based gas turbines. These hot-section components include a combustion chamber, blades, and vanes. The TBC leads to significant reduction of heat transfer from the high temperature gas to metal surface. As a result, with increase of operating temperature inside the gas turbines, their efficiency would be improved notably. Typically, a TBC system exhibits multilayer added structure, consisting of a bond coat and a top coat. The top coat is thermally resistant, whereas the bond coat can serve to be oxidation resistant. As two key performances, the function of thermal insulation and the durability against spallation during thermal service guide the material selection, structural tailoring, as well as process optimization of TBC. These two performances depend highly on properties of the ceramic top coat of TBC. Given that, materials and structure of the top coat are critically important for the development of advanced TBCs.