Temperature dependence mechanism of high-temperature oxidation of transition metal silicide MoSi.

Transition metal silicides represented by MoSihave 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 MoSioxidation products has not been revealed. Therefore, this study investigated the formation characteristics of oxide film and silicide-poor compound on MoSiat 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 MoSiunderwent high-temperature selective oxidation reactions at 1000 °C-1200 °C, forming MoOand SiOoxide film on the substrate. As the oxidation temperature increased to 1550 °C, after 100 h of oxidation, along with the disappearance of MoOand the phase transformation of SiO, a continuous MoSilayer with a thickness of approximately 47m was formed at the SiO-MoSiinterface. Thermodynamics and kinetic calculations further revealed the mechanism of temperature-dependent growth of oxidation products (MoOand MoSi) during high-temperature oxidation process of MoSi. 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 MoSilayer. Its thickness is an important indicator for evaluating the oxidation resistance of MoSicoatings during service. This study provides experimental and mechanistic insights into the temperature-dependent growth behavior of MoSiduring the high-temperature oxidation of MoSicoating, and provides guidance for predicting the service life and improving the oxidation resistance of silicide coatings.