Oxidation behavior of plasma-sprayed MoSi2-Yb2O3 composite coating at 1700 °C

Rare earths with unique electronic structure and properties have incomparable advantages for modifying the comprehensive performance of silicide materials. In this study, MoSi2-based composite coatings with different rare-earth Yb2O3 contents were prepared using supersonic atmospheric plasma spraying, and their microstructural features and oxidation behavior at 1700 degrees C were investigated systematically. Results showed that the sprayed MoSi2-Yb2O3 composite coating possessed the dense structure without visible defects and tightly adhered to the SiC transition layer. During oxidation at 1700 degrees C, all the samples exhibited an explicit linear oxidation mode, in which the MoSi2-10 wt%Yb2O3 coating qualified the optimal oxidation resistance with the lowest specific mass loss relative to other coatings. It was natural to consider that the Yb2O3 dopant changed the microstructural aspects of the formed oxide scale upon oxidation, and then affecting the oxidation behavior of the applied coating. Moderate doping of Yb2O3 stabilized the Si-O covalent bonds in SiO2 network, leading to the enhanced viscosity of oxide glass scale, thereby delaying the effective delivery of oxygen molecules as well as the oxidation degradation of the coating.