High-temperature corrosion mechanism of a promising scandium tantalate ceramic for next generation thermal barrier coating under molten calcium–magnesium-aluminosilicate (CMAS)

Abstract

Hot corrosion caused by molten calcium–magnesium-aluminosilicate (CMAS) is one of the significant failure factors of thermal barrier coating (TBC). Scandium tantalite (ScTaO4) is expected to be a next generation of TBC material because of its great thermophysical characteristics. This study focused on high-temperature corrosion behaviors of ScTaO4 ceramic exposure to molten CMAS at 1300 °C. During corrosion experiments, a clear but discontinuous reaction layer containing CaTa2O6 and Sc2SiO5 was observed, which was formed by dissolution reprecipitation. In addition, ScTaO4 showed good phase stability and maintained monoclinic wolframite structure with P2/c (13) space group in the corrosion tests. Moreover, Ca, Mg and Al were all kept away from the ScTaO4 ceramic due to low solubility of Sc3+ in the CMAS. Therefore, ScTaO4 ceramic owns great ability to resist the corrosion of CMAS. Good phase stability enables ScTaO4 to stably exist at high temperature, reducing volume change, thus extending the service life of the coating. Meanwhile, great corrosion resistance of CMAS reduces the consumption of ScTaO4 under adverse environmental conditions, further extending the service life of the coating. In summary, ScTaO4 is a new kind of potential thermal barrier material to replace YSZ ceramic.