Microstructures andoxidation resistance of MoSi ₂ coating prepared by low pressure chemical vapor deposition

To prevent Mo alloy from oxidation, a MoSi ₂ coating has been prepared by low pressure chemical vapor deposition (LPCVD). Microstructures of the coating were studied through XRD, SEM, EDS. The isothermal oxidation and thermal shock of the coating was also tested. Results show that the MoSi ₂ coating has compact structure with only a few microcracks and exhibites a nice thermal shock resistance and anti-oxidation ability. The coated samples have just a 0.3% weight loss after 20 times thermal shocks. No spalling and splitting appear in the coating. For 180 h isothermal oxidation at 1300°C, the weight loss of sample is less than 0.83%. The weight loss is mainly owing to the generation of volatile MO, MoO ₂ and MoO ₃ by the reaction between the oxygen diffused in and Mo at the interface between the coating and matrix.