Oxidation behavior of Ti3Al-xNb (x = 0, 3, 7, 11, 13 at%) at 1073-1273 K in air

Titanium aluminide (Ti3Al-Nb) has potential for high temperature applicatio ns because of its low density and high temperature strength. The isothermal oxidation behavior of Ti3Al containing 3-13 at%Nb was investigated in air over the temperature range of 1073-1273 K using thermogravimetric analysis. Oxide products were identified using X-ray diffraction and energy dispersi ve x-ray analysis. Surface morphology of oxide scales and cross-sections of oxidizied specimens were examined using scanning electron microscopy. At 1 073 K, the difference of the mass gain between Nb-free Ti3Al and Nb contain ing Ti3Al is not very obvious. However, the remarkable decrease in oxidatio n rates was observed for Ti3Al-11Nb and Ti3Al-13Nb alloys at 1173 and 1273 K. The oxide scales of Ti3Al-11Nb and Ti3Al-13Nb were compact and multilaye red, and consisted primarily of TiO2 doped with Nb, and a layer of Al2O3. F or Ti3Al, the oxide layer consisted of pillar-like TiO2 and was porous. A N b-rich layer was found adjacent to the substrate for Nb containing Ti3Al al loys.