Improvement in oxidation resistance of TiB₂ by formation of protective SiO₂ layer on surface

To improve the oxidation resistance of TiB₂ material, dense silica (SiO₂) layer was caused to form on the surface. The coating layer was formed on the surface by exposing the specimens next to a bed of SiC powder in a flowing H₂ containing 0.1% H₂O at 1450 °C. Part of SiO₂ “smoke”, generated by a reaction between the SiC powder and H₂O in the H₂ gas stream, was deposited on the sample surface to form a dense and uniform SiO₂ layer. Beneath the SiO₂ layer, an interfacial layer composed of Ti₂O₃ and B₂O₃was formed. Oxidation resistance of the specimen was improved markedly by the coating layers. The coating layers enhanced the oxidation resistance through the retardation of oxygen transport and also through the consumption of oxygen by a reaction with Ti₂O₃ to form TiO₂.