Chemical reaction of ceramic coatings of Ti-Si-C system on Ti-5Al-2.5Sn substrate prepared by tungsten inert-gas arc cladding

The surface ceramic coatings were prepared on Ti-5Al-2.5Sn substrate by tungsten inert-gas arc depositon process. The microstructures and phases were analyzed using the method of SEM and XRD for the cladding coatings of Ti-SiC and Ti-SiC-C systems. Moreover, the changes of Gibbs energy for possible reactions in systems were calculated using thermodynamic analysis. The results shows that the main microstructure are composed with dendritic TiC and needle-shaped or chrysanthemum Ti₅Si₃ in the cladding coating of Ti-SiC system, the reaction mechanism is 8Ti+3SiC→3TiC+Ti₅Si₃. However, in Ti-SiC-C system, there are TiSi₂ and Ti₃SiC₂ hybrid microstructure observed besides TiC. 6Ti+3SiC+C→Ti₃SiC₂+TiSi₂+2TiC is the main reaction mechanism. In addition, the addition of graphite in Ti-SiC system favors to the generation of self-lubricating Ti₃SiC₂ phases, while the brittle Ti₅Si₃ phases are avoided.