Influence of aluminium addition on oxidation resistance of Ta-W alloy

Alloys with composition of Ta-10 wt.% W and Ta-10 wt.% W-6 wt.% Al, respectively, were prepared by the hot-press sintering process. The oxidation behaviour at 900°C and 1000°C was studied. The oxidation weight gain curves of the Ta–10%W alloy followed the linear law and the final oxidation product was Ta₂O₅ solid solution. Meanwhile, due to the addition of Al, the oxidation weight gain curves of the Ta–10%W–6%Al alloy followed the parabolic law. The final oxidation products at 900°C formed a dense outer layer Al₂O₃ and an inner layer. However, after being oxidised at 1000°C, the oxidation products included Al₂O₃, AlTaO₄ and Ta₂₂W₄O₆₇. Since the dense Al₂O₃ oxide film was consumed by the generation of AlTaO₄, the inward diffusion of oxygen cannot be prevented. The oxidation resistance degraded at 1000°C. The addition of Al significantly improved the oxidation resistance of the Ta-W-based alloy system.