High temperature oxidation behavior of molybdenum borides by silicon pack cementation process

In this study, high temperature oxidation behavior of molybdenum borides by pack cementation process was investigated. Silicon (Si) pack cementation process of molybdenum borides was performed at 1100 °C for 5 h. Silicide layers including MoSi₂ phase were formed on the surface of molybdenum borides by Si pack cementation process. The thickness of silicide layer was about 70.12 μm. Molybdenum borides and pack cemented Molybdenum borides was oxidized at 1000 °C for up to 50 h. Molybdenum borides without pack cementation process was severely oxidized and its weight was reduced by approximately 87% compared to the initial weight due to the evaporation of MoO₃ phase. On the other hand, pack cemented molybdenum borides were much less oxidized. In pack cemented molybdenum borides, dense borosilicate layer was formed at the surface, and this layer effectively suppressed continuous oxidation and evaporation of MoO₃ phase. Based on these results, we demonstrated that the cause of this difference depends on the coating layer formed on the surface by pack cementation process, and Si pack cementation process is effective in improving the oxidation resistance of molybdenum borides.