Effect of Ti content and annealing on microstructure and mechanical performance of plasma sprayed Ti–Al–C based composite coatings

In the work, Ti–Al–C composite coatings have been produced by plasma spraying graphite @ Ti–Al agglomerates with different Ti content and then Ar-annealed at 800 °C. The microstructure change, phase formation mechanism and mechanical performance of the coatings have been studied. Results displayed that these coatings mainly consisted of (Ti, Al)C, TiC, a small amount of Ti2AlC/Ti3AlC2 and residual Al. These phases were alternatively arranged to form a lamellar structure. After annealing, the Ti2AlC/Ti3AlC2 phase increased with the consumption of (Ti, Al)C and residual Al. Owing to the difference of initial phase composition affected by Ti content, post-annealing generated (Ti, Al)C/TiC–Ti2AlC and (Ti, Al)C/TiC–Ti3AlC2 composite coatings inT2.5AC800 and T1.0AC800 coating, respectively. The laminated structure was hardly changed by annealing. The T2.5AC (970 HV) coating showed higher hardness than the T1.0AC coating (464 HV). After annealing, the hardness of the former coating increased while the latter coating decreased. Both of phase structure and uniformity determined the coating hardness.