A new strategy to fabricate Ti2AlC MAX coatings by the two-step laser method

Abstract

High-content Ti2AlC MAX coatings were efficiently prepared on TC4 plates by two-step laser method (laser cladding and post-laser treatment). The microstructure and phase composition of the coatings were analyzed, and the in-situ synthesis mechanism of MAX phases was explored. According to the results, the diffusion of Al atoms in the cladded coatings led to the formation of a core-shell structure with TiC as the core and Ti2AlC as the shell. During post-laser treatment, the diffusion of C and Al atoms was intensified, which facilitated the nucleation-growth of the Ti2AlC phase, producing two types of MAX phase structures. The short rod-shaped MAX phase was precipitated directly from the coating matrix, while the blocky MAX phase gradually formed owing to atomic diffusion. Finally, the content of Ti2AlC MAX phase in as-obtained coatings after post-laser treatment at the laser power of 1.2 kW and the scanning speed of 1 mm/s reached 82.93 wt%, which was 9.03 times higher than that in the cladded coating. Therefore, the two-step laser technique proposed in this work enables the production of high-content MAX coatings, which opens up new prospects for efficient preparation of MAX phase coatings and related structures.