Oxidation behavior and kinetics of in situ (TiB2+TiC)/Ti3SiC2 composites in air

The isothermal oxidation behavior of in situ (TiB2+TiC)/Ti3SiC2 composite ceramics with different TiB2 content has been investigated at 900–1200°C in air for exposure times up to 20h by means of X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. The oxidation of (TiB2+TiC)/Ti3SiC2 composites follows a parabolic rate law. With the increase in TiB2 content, the oxidation weight gain, thickness of the oxidation scale, and parabolic rate constant decrease dramatically, which suggests that the incorporation of TiB2 greatly improves the oxidation resistance of the composites. With the increase in oxidation temperature, the enhancement effect becomes more pronounced. Due to the incorporation of TiB2, the oxidation scale of (TiB2+TiC)/Ti3SiC2 composites is generally composed of an outer layer of coarse-grained TiO2 and an inner layer of amorphous boron silicate and fine-grained TiO2. Only the dense inner layer formed on the surface acts as a diffusion barrier, retarding the inward diffusion of O, and consequently contributing to the improved oxidation resistance of the (TiB2+TiC)/Ti3SiC2 composites.