Effect of Molten Al/Si Impregnation on the Oxidation Resistance of TiB₂ at 1300°C

Abstract

Despite their superior material properties at high temperatures, the poor oxidation resistance of borides such as TiB₂ above 1000°C limits their applications. Herein, we demonstrate the liquid-phase impregnation of Al or Si into the sintered compact of TiB₂ and study their effect on the oxidation behavior at 1300°C. The thermogravimetric curves obtained under oxidation and subsequent crystal phase identification suggest that Al impregnation can prevent the evaporation of boron oxide by forming aluminum borate, which is an unstable protective layer, resulting in a slight increase in the oxidation resistance. By contrast, the Si-impregnated specimens showed lesser mass change due to oxidation than that in the unimpregnated specimens, owing to the formation of a stable protective SiO₂ phase on the sample surface. Hence, molten Si impregnation of sintered borides is a promising new approach for improving high-temperature oxidation resistance.

Fig. 5 Schematics of oxidation processes for TiB₂ without and with the impregnation of Al/Si.