Microstructure and Antioxidative Performance of Y2O3-CeO2 Co-Modified Molybdenum Silicide Coatings

To enhance the high-temperature oxidation resistance of molybdenum-based materials, Y2O3-CeO2 co-modified silicide coatings were produced on molybdenum substrates using two-step pack cementation. The microstructure and phase composition of Y2O3-CeO2 co-modified composite coatings were examined both before and after oxidation. A detailed analysis of the antioxidant properties of the co-modified coatings and the mechanisms behind the modifications was also conducted. The incorporation of 1.0 wt.% CeO2 and 1.5 wt.% Y2O3 into the composite coatings resulted in a dense, non-porous, maximum-thickness microstructure. This microstructure is characterized by the uniform distribution of parallel MoSi2 and MoB layers on the substrate. In particular, the coating containing 1.5 wt.% Y2O3 exhibited superior oxidation resistance, with a weight gain of 0.29 mg/cm2 and an oxidation rate constant of 6.68 × 10−4 mg2/(cm4·h) after oxidation at 1150 °C for 255 h. During oxidation, a dense SiO2 oxide film is formed through the cooperation of Y2O3 and CeO2, inhibiting further Si diffusion into the substrate and reducing the formation of the Mo5Si3 layer.