Synthesis, sintering, and effect of surface roughness on oxidation of submicron Ti 2 AlC ceramics

Submicron Ti 2 AlC MAX phase powder was synthesized by molten salt shielded synthesis (MS 3 ) using a Ti:Al:C molar ratio of 2:1:0.9 at a process temperature of 1000°C for 5  hours. The synthesized powder presented a mean particle size of ~0.9 µm and a purity of 91 wt. % Ti 2 AlC, containing 6 wt. % Ti 3 AlC 2 . The Ti 2 AlC powder was sintered by pressureless sintering, achieving a maximal relative density of 90%, hence field‐assisted sintering technology/spark plasma sintering was used to enhance densification. The fine‐grained microstructure was preserved, and phase purity of Ti 2 AlC was unaltered in the latter case, with a relative density of 98.5%. Oxidation was performed at 1200°C for 50 hours in static air of dense monolithic Ti 2 AlC with different surface finish, (polished, ground and sandblasted) which resulted in the formation of an approx. 8 µm thin aluminum oxide (Al 2 O 3 ) layer decorated with titanium dioxide (rutile, TiO 2 ) colonies. Surface quality had no influence on Al 2 O 3 scale thickness, but the amount and size of TiO 2 crystals increased with surface roughness. A phenomenon of rumpling of the thermally grown oxide (TGO) was observed and a model to estimate the extent of deformation is proposed.