Temperature dependence mechanism of high-temperature oxidation of transition metal silicide MoSi2

Abstract Transition metal silicides represented by MoSi 2 have excellent oxidation resistance and are widely used as high-temperature anti-oxidation coatings in hot end components of power equipment. However, the mechanism of temperature-dependent growth of MoSi 2 oxidation products has not been revealed. Therefore, this study investigated the formation characteristics of oxide film and silicide-poor compound on MoSi 2 at temperatures of 1000 °C–1550 °C through high-temperature oxidation experiments, combined with microscopic Raman spectroscopy, scanning electron microscope, and x-ray diffraction (XRD) characterizations. The result showed that MoSi 2 underwent high-temperature selective oxidation reactions at 1000 °C–1200 °C, forming MoO 2 and SiO 2 oxide film on the substrate. As the oxidation temperature increased to 1550 °C, after 100 h of oxidation, along with the disappearance of MoO 2 and the phase transformation of SiO 2 , a continuous Mo 5 Si 3 layer with a thickness of approximately 47 μ m was formed at the SiO 2 –MoSi 2 interface. Thermodynamics and kinetic calculations further revealed the mechanism of temperature-dependent growth of oxidation products (MoO 2 and Mo 5 Si 3 ) during high-temperature oxidation process of MoSi 2 . As the temperature increased, the diffusion flux ratio of O and Si decreased, leading to a decrease in oxygen concentration at the interface and promoting the growth of the Mo 5 Si 3 layer. Its thickness is an important indicator for evaluating the oxidation resistance of MoSi 2 coatings during service. This study provides experimental and mechanistic insights into the temperature-dependent growth behavior of Mo 5 Si 3 during the high-temperature oxidation of MoSi 2 coating, and provides guidance for predicting the service life and improving the oxidation resistance of silicide coatings.