Hot corrosion behavior of nanostructured Gd₂O₃ doped YSZ thermal barrier coating in presence of Na₂SO₄ + V₂O₅ molten salts

Nickel-based superalloy DZ125 was first sprayed with a NiCrAlY bond coat and followed with a nanostructured 2 mol% Gd₂O₃−4.5 mol% Y₂O₃-ZrO₂ (2GdYSZ) topcoat using air plasma spraying (APS). Hot corrosion behavior of the as-sprayed thermal barrier coatings (TBCs) were investigated in the presence of 50 wt% Na₂SO₄ + 50 wt% V₂O₅ as the corrosive molten salt at 900 °C for 100 h. The analysis results indicate that Gd doped YVO₄ and m-ZrO₂ crystals were formed as corrosion products due to the reaction of the corrosive salts with stabilizers (Y₂O₃, Gd₂O₃) of zirconia. Cross-section morphology shows that a thin layer called TGO was formed at the bond coat/topcoat interface. After hot corrosion test, the proportion of m-ZrO₂ phase in nanostructured 2GdYSZ coating is lower than that of nano-YSZ coating. The result reveals that nanostructured 2GdYSZ coating exhibits a better hot corrosion resistance than nano-YSZ coating.