Wear rate of titanium matrix composite coating at high temperature further increased by non-stoichiometric Ti_xC oxidation

Elevated-temperature tribological behaviors of titanium matrix composite (TMC) coatings are investigated. Results indicate that TMC coatings experience increased wear rates at 500 °C combined with ploughing, delamination, and oxidation wear mechanisms. The hybrid TiB + TiC reinforced Ti64 composite coating shows a higher wear rate than composite solely reinforced by TiB at 500 °C. Nevertheless, the hybrid TMC coating exhibits a relatively lower wear rate at room temperature. In addition, it has been revealed that the reverse order of wear rate is attributed to the non-stoichiometric characteristic of the Ti_xC ceramic phase in hybrid composite, which is preferentially oxidized at elevated temperature, leading to the remarkable decrease of wear resistance. Meanwhile, the high thermal stability of TiB ceramic contributes to the low wear rate of TiB/Ti6Al4V coating at 500 °C.