A Comparative Study on Hot Corrosion Resistance of Several Types of Thermal Barrier Coatings: YSZ, CSZ, Mullite and YSZ+Al2O3

Hot corrosion is one of the main destructive factors in thermal barrier coatings (TBCs) which comes as a result of molten salt effect on the coating–gas interface. Hot corrosion tests were carried out on the surface of coatings in molten salt (Na₂SO₄ +V₂O₅) at 1000 ◦C for 48 h. Spallation was observed in TBCs. The formation of monoclinic ZrO₂ and YVO₄ crystals as hot corrosion products caused the degradation of mentioned TBCs. Although monoclinic
ZrO₂ decreased in (YSZ +Al2O3) in comparison with usual YSZ, dendritic YVO₄ crystals had main role in degradation of (YSZ +Al2O3) coating. Results revealed that CSZ TBCs were better resistant to hot corrosion environment than YSZ  TBCs in terms of phase stability and overall damage by the salt. From the present results, a possible microscopic degradation mechanism and effects of coating microstructures for zirconia-based TBCs under hot corrosion are discussed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to investigate structure and microstructural characterizations