The effect of Ta on oxidation resistance of TiC/hastelloy composites

The oxidation resistance is pivotal to TiC/hastelloy composites applied for high-temperature structural components. In this paper, the effect of Ta on oxidation resistance of TiC/hastelloy composites was investigated. Composites with different Ta contents were prepared by reactive infiltration method, and the oxidation test was held at 800 degrees C for 100 h in air. The result indicates that as Ta content increases from 1 to 8 wt%, the mass gain decreases from 0.48 to 0.30 mg cm(-2), demonstrating that the oxidation resistance of composites is optimized. The oxide scale changes from sandwich structure to thinner bilayer with CrTaO4. Ta decreases the initial oxidation rate of TiC and metal matrix, while Ta promotes the formation of continuous Cr2O3 layer. After oxidation, Ta mainly dopes in TiO2 and Cr2O3 with 1 wt% Ta, while CrTaO4 is found in oxide scale with 8 wt% Ta. Ta-doped TiO2 inhibits the inward diffusion of O, and CrTaO4 suppresses the outward diffusion of Ni, Ti and Cr. Therefore, the oxide scale with CrTaO4 on TiC/hastelloy composites exhibits better protective effect.