Surface strengthening of Ti3SiC2 through magnetron sputtering Cu and subsequent annealing

Magnetron sputtering deposition Cu and subsequent annealing in the temperature range of 900–1100 °C for 30–60 min were conducted with the motivation to modify the surface hardness of Ti3SiC2. Owing to the formation of TiC following the reaction Ti3SiC2 + 3Cu → 3TiC0.67 + Cu3Si, the surface hardness was enhanced from 5.08 GPa to a maximum 9.65 GPa. In addition, the surface hardness was dependent on the relative amount of TiC, which was related to Cu film thickness, heat treatment temperatures and durations of annealing. Furthermore, after annealing at 1000 °C for 30 min the Cu-coated Ti3SiC2 has lower wear rate and lower COF at the running-in stage compared with Ti3SiC2 substrate. The reaction was triggered by the inward diffusion of Cu along the grain boundaries and defects of Ti3SiC2. At low temperature and short annealing time, i.e. 900 or 1000 °C for 30 min, Cu diffused inward Ti3SiC2 and accumulated at the trigonal junctions first. At higher temperature of 1100 °C or prolonging the annealing time to 60 min, considerable amount of Cu diffused to Ti3SiC2 and filled up the grain boundaries leaving a mesh structure.