Bond Coat Oxidation and Hot Corrosion Behavior of Plasma Sprayed YSZ Coating on Ni Superalloy

Oxidation and hot corrosion are considered as two main destructive factors in thermal barrier coatings (TBCs). The mechanisms of bond coat oxidation and hot corrosion of yttria stabilized zirconia (YSZ) plasma sprayed coatings were evaluated. Oxidation tests were carried out at 1100℃ for 22,42 and 100h. Hot corrosion tests were performed on the coating in molten salt (Na₂SO₄+V₂O₅) at 1050℃ for 40h. Spallation was observed at the bond coat/YSZ interface after 100h oxidation. Micro XRD analysis after the oxidation test revealed the formation of destructive oxides such as NiCr₂O₄, NiCrO₃ and NiCrO₄ within the bond coat of YSZ coating. XRD and SEM studies after hot corrosion demonstrated the formation of monoclinic ZrO₂ and YVO₄ crystals as hot corrosion products, which caused the degradation of YSZ coating.