Vanadium-induced hot corrosion behavior of 8YSZ and MgO-modified 8YSZ composite powders at 1100°C

Isothermal hot corrosion behavior of 8 yttria-stabilized zirconia (8YSZ) and a newly developed MgO/8YSZ composite powder was investigated in the presence of 5 wt% V₂O₅. Hot corrosion tests were performed at 1100°C in a high-temperature furnace for a total duration of 10 h. The samples were removed and air-cooled after every 2 h for a total duration of 10 h. The microstructure, elemental composition and phase evolution of the specimens after exposure were characterized by field emission scanning electron microscopy (FESEM) with energy dispersive spectroscopy (EDS) and X-ray diffractometer (XRD), respectively. Results showed that the dominant hot corrosion mechanism of 8YSZ in V₂O₅ at 1100 °C was the destabilization of 8YSZ, owing to the reaction between Y₂O₃ and V₂O₅ resulting in the formation of YVO₄. The predominant tetragonal structure of 8YSZ was therefore transformed to monoclinic phase. However, the addition of MgO to 8YSZ in various ratios (5, 10, and 15 wt%) showed significant improvement in the hot corrosion performance by impeding the reaction between V₂O₅ and Y₂O₃ through the formation of magnesium orthovanadate. It was, however, observed that the effectiveness of the composite is dependent on the thermal stability of the vanadate formed. Magnesium orthovanadate trapped free vanadium, thereby preventing it from interacting with the yttria stabilizer in 8YSZ. The degradation mechanisms followed the Lewis acid base theory.