Degradation of Thermal Barrier Coatings by Fuel Impurities and CMAS

This study investigates the degradation of YSZ-CoNiCrAlY thermal barrier coatings (TBCs) due to vanadium and phosphorus pentoxides and calcium-magnesium aluminosilicate (CMAS) sand at temperatures up to 1400 °C. The pentoxides are shown to degrade bond coat and topcoat layers through acidic dissolution, while CMAS sand is shown to degrade YSZ layers through ingress and the precipitation of ZrO₂ grains. Density functional theory simulations provide insights on reactions at the surface of fluorite-structured oxides and the role of oxygen vacancy clustering. A method to mitigate melt-infiltration attack through electrophoretic deposition is introduced.