High-Temperature Oxidation Resistance and Molten Salt Corrosion Study of YSZ, CeYSZ, and YSZ/CeYSZ Thermal Barrier Coatings by Atmospheric Plasma Spraying

Five thermal barrier coatings (TBCs), namely TBC-1 (YSZ), TBC-2 (CeYSZ), TBC-3 (YSZ:CeYSZ = 1:2), TBC-4 (YSZ:CeYSZ = 1:1), and TBC-5 (YSZ:CeYSZ = 2:1), were fabricated using the atmospheric plasma spraying (APS) method. Their oxidation behaviors at 1100 °C and corrosion resistance to molten salts (V2O5 + Na2SO4) at 900 °C were examined. After 100 h of oxidation, the thermally grown oxide layer (TGO) for YSZ primarily contained Cr and Ni oxides with significant internal fractures, presenting a continuous band-like Al2O3. In dual-ceramic configurations, an increase in CeYSZ thickness led to a rise in Al content and reduced Cr and Ni in TGO, with the surface fracture morphing into an internal porosity. Following salt corrosion, YSZ revealed rod-like YVO4 and m-ZrO2 as corrosion products, whereas CeYSZ displayed chain-structured CeO2, CeYO4, and YVO4 combined with m-ZrO2. YSZ coatings underwent notable phase transitions with evident densification, forming a corrosion layer of approximately 10 μm. Conversely, CeYSZ showed a limited phase change, retaining porosity without a distinguishable corrosion layer. As CeYSZ thickness increased from 100 μm to 200 μm in the dual-ceramic structure, salt penetration reduced. Evidently, the dense structure of CeYSZ heightened diffusion resistance against oxygen and corrosive salts, rendering superior oxidation and corrosion resistance over YSZ. By optimizing the thickness ratio between CeYSZ and YSZ, whilst retaining total ceramic layer thickness, the dual-ceramic TBC’s resistance to high-temperature oxidation and corrosion can be enhanced.