Effects of Al and refractory alloying elements (W, Ta and Hf) on oxidation kinetics, oxygen dissolution and diffusion in titanium alloys
Abstract
The effect of aluminium, tungsten, tantalum and hafnium on the oxidation behaviour of titanium was investigated. Model alloys were oxidized in air for 5000 h at 650°C. All alloying elements decreased oxide growth and oxygen dissolution in the metal; tungsten was the most efficient. The oxygen diffusivity decreased with aluminium. Tungsten enhanced the formation of Ti$_2$N at the oxide/metal interface which decreased oxygen dissolution in the alloys. Experiments in Ar-20%O$_2$, where Ti$_2$N could not form, confirmed the major role of nitrogen on the oxidation resistance of tungsten-containing alloys. The ternary model alloy Ti-10Al-2W outperformed the high-temperature alloy Ti6242S.