Insights into the high-temperature oxidation of MAX phases: The effect of TiC impurities in Ti3AlC2

Ti 3 AlC 2 MAX phase is a premier candidate for high-temperature applications due to its ability to form a protective α-Al 2 O 3 layer. However, the influence of common synthesis byproducts, particularly TiC, on intrinsic oxidation resistance remains insufficiently understood. To this end, a series of samples was fabricated by reactive spark plasma sintering with precise stoichiometric control to systematically investigate the determinative effect of TiC secondary phase (0–21 wt%) on the isothermal oxidation of Ti 3 AlC 2 at 1200 °C, as assessed by thermogravimetric analysis (TGA) and microstructural examination. Results reveal that while phase-pure Ti 3 AlC 2 exhibited exceptional oxidation resistance through parabolic growth of a continuous, 3 µm-thick adherent α-Al 2 O 3 layer, the presence of TiC triggered a transition toward destructive linear kinetics. Notably, a 21 wt% TiC content resulted in a 46-fold increase in mass gain per unit area and the formation of a porous, non-protective TiO 2 -rich layer nearly 500 µm thick. Identical-location microstructural analysis of a TiC-rich sample at initial stages of oxidation demonstrated how TiC grains act as preferential nucleation and growth sites for TiO 2 , compromising the MAX phase inherent passivation and self-healing capabilities. These findings highlight the critical importance of phase purity in optimizing MAX phases for reliable oxidation resistance performance in demanding high-temperature environments.