Hot Corrosion Behavior of Multi-Layer Suspension Plasma Sprayed Gd₂Zr₂O₇/YSZ Thermal Barrier Coatings

This study investigates the corrosion resistance Gd₂Zr₂O₇/YSZ coatings and a YSZ layer of similar thickness. All coatings were produced by suspension plasma spraying, resulting in a columnar structure. Corrosion tests conducted at 900 °C for 8 h in a molten salt bath show that Gd₂Zr₂O₇ is not as corrosion resistant as YSZ. Molten salts react with Gd₂Zr₂O₇ producing GdVO₄ along the surface as well as between the columns of the coating. The formation of GdVO₄ between the columns, in combination with the low fracture toughness of Gd₂Zr₂O₇, is likely responsible for the lower corrosion resistance. Furthermore, the presence of another layer of Gd₂Zr₂O₇ on top of the Gd₂Zr₂O₇/YSZ coating, to prevent salt infiltration, did not improve corrosion resistance.