High Temperature Oxidation Mechanism of TiAl-W-Si Alloys
The oxidation of Ti-(43~52%)Al-2%W-(0~0.5%)Si alloys between 900 and 1050°C in air progressed via the outward diffusion of Ti ions to form the outer TiO2 layer, and the inward transport of oxygen to form the inner (TiO2+Al2O3) mixed layer, between which the intermediate Al2O3 barrier layer existed. Tungsten tended to diffuse inward to be incorporated below the intermediate Al2O3 layer, while Si outward to exist over the entire oxide layer. Both W and Si tended to be dissolved in the oxide layer, rather than forming independent oxides.
S.-G. Kang and T. Kobayashi
D. B. Lee and S. W. Woo, "High Temperature Oxidation Mechanism of TiAl-W-Si Alloys", Materials Science Forum, Vols. 449-452, pp. 817-820, 2004