Understanding the growth mechanisms of TiO2/Al2O3 mixed scales formed on Al-depleted Ti2AlC at 1000–1200 °C

Abstract

We present a detailed study of thermally grown oxide scales on a bulk Ti2AlC material and explore its oxide growth mechanisms at 1000 °C, 1100 °C and 1200 °C, respectively. The oxide scale predominantly consists of an outer TiO2-rich layer and an inner TiO2/Al2O3 mixed layer. The formation of such a duplex microstructure is caused by the phase transformation from Ti2AlC to TiC at the scale/substrate interface and the Al depletion due to the formation of impurities. The insufficient supply of Al to scale/substrate interface, together with the competition from growth of TiO2, prevents formation of a continuous Al2O3 scale.