Oxidation resistance of Ti3AlC2 and Ti3Al0.8Sn0.2C2 MAX phases: a comparison

Ti3AlC2 and Ti3Al0.8Sn0.2C2 MAX phase powders are densified using Spark Plasma Sintering (SPS) technique to obtain dense bulk materials. Oxidation tests are then performed over the temperature range 800 degrees C-1000 degrees C under synthetic air on the two different materials in order to compare their oxidation resistance. It is demonstrated that, in the case of the Ti3Al0.8Sn0.2C2 solid solution, the oxide layers consist in TiO2, Al2O3, and SnO2. The presence of Sn atoms in the A planes of the solid solution leads to an easy diffusion of Sn out of the MAX phase which promote the formation of the nonprotective and fast growing SnO2 oxide. Moreover, the small Al/Ti atom's ratio promotes the growth of a nonprotective rutile-TiO2 scale as well. In the case of the Ti3AlC2 MAX phase, the oxide layer consists in a protective alumina scale; a few TiO2 grains being observed on the top of the Al2O3 layer. The parabolic oxidation rate constants are about 3 orders of magnitude smaller for Ti3AlC2 compared to Ti3Al0.8Sn0.2C2.