High-temperature oxidation response of Mo-Si-B composites with TiO2w/SiCw addition

In this study, TiO2w addition improved the oxidation resistance of the Mo-Si-B composite at 1300 degrees C. The TiO2 partially dissolved in SiO2 modified the network structure of the SiO2 glass and improved its fluidity at the initial oxidation stage. This favored to a continuous scale cover on the surface of the Mo-Si-B composite rapidly. The residual TiO2w promoted the formation of a passivated multilayer borosilicate scale at current temperature, which could impede the MoO3 volatilisation and O diffusion at the stable oxidation stage. The SiCw addition, compared to the TiO2w, especially could ensure the Mo-Si-B-SiC composite withstand a higher temperature such as 1400 degrees C. Its oxidation and the more intermetallics in the composite could increase the number of active sites of the SiO2 glass, thereby supplying the borosilicate scale with a relatively sufficient Si element. Thus, the transient oxidation stage was minimised and the initial mass loss was reduced, which indicated a continuous borosilicate scale had formed quickly at the initial stage. Finally, the improved viscosity of the borosilicate due to a lower B/Si ratio, could obviously decreased the oxygen diffusion and enabled the formation of a protective borosilicate layer at or above 1400 degrees C.