Influence of Iron Oxide Deposits on the Hot Corrosion Resistance of YSZ Thermal Barrier Coatings in Molten Vanadium Pentoxide

ABSTRACT The effect of iron oxide (Fe₂O₃) deposits on the hot corrosion (HC) mechanisms of yttria‐stabilized zirconia (YSZ) thermal barrier coatings in the presence of vanadium oxide was investigated. The experiments involved exposing YSZ samples to vanadium pentoxide (V₂O₅) at 900°C for 90 min, both with and without the addition of Fe₂O₃. Surface and cross‐sectional analyses of the samples were conducted using optical microscopy, scanning electron microscopy (SEM/EDS), and X‐ray diffraction. Additionally, the porosity and delamination percentages of the thermal barrier coatings were quantified through digital image processing techniques. The primary damage mechanisms identified included yttria dissolution, which facilitated the tetragonal‐to‐monoclinic phase transformation of YSZ, as well as the infiltration of V₂O₅ through cracks and pores, leading to coating delamination near the Top Coat/Bond Coat (TC/BC) interface. Notably, Fe₂O₃ reacted with V₂O₅ during the tests, forming an iron‐vanadium oxide (FeV₃O₈). Furthermore, the presence of Fe₂O₃ increases the HC attack, reducing the tetragonal phase content of the YSZ coating.