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.