High temperature oxidation behaviour of Ti2AlC ceramic at 1200°C

The oxidation process of Ti2AlC ceramics in dry synthetic air at 1200 degrees C was monitored with thermogravimetry. The microstructural evolution of the oxide scale with time was characterised by Xray diffractometry, scanning electron microscopy, X-ray microanalysis and electron back scattering diffraction. The oxide scale is comprised of a continuous alpha-Al2O3 inner layer with isolated coarse TiO2 particles on top. At the early oxidation stage (roughly less than 0.5 h), alpha-Al2O3 and TiO2 are the main reaction products, while at longer reaction times the oxidation only leads to the formation of alpha-Al2O3. The alpha-Al2O3 grains in the oxide scale grow in size upon high-temperature oxidation with the grain size being uniform throughout the thickness of the scale. As diffusion of oxygen along the grain boundaries dominates the oxide scale growth, the change in grain size affects the oxide scale growth kinetics. A simple oxide scale growth model, that takes into account this change in fast diffusion paths, describes the experimentally observed oxide scale growth kinetics perfectly.