Magnetron sputtering deposition Cu and subsequent annealing in the temperature range of 900–1100°C for 30–60min were conducted with the motivation to modify the surface hardness of Ti 3 SiC 2 . Owing to the formation of TiC following the reaction Ti 3 SiC 2 +3Cu→3TiC 0.67 +Cu 3 Si, the surface hardness was enhanced from 5.08GPa to a maximum 9.65GPa. 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 30min the Cu-coated Ti 3 SiC 2 has lower wear rate and lower COF at the running-in stage compared with Ti 3 SiC 2 substrate. The reaction was triggered by the inward diffusion of Cu along the grain boundaries and defects of Ti 3 SiC 2 . At low temperature and short annealing time, i.e. 900 or 1000°C for 30min, Cu diffused inward Ti 3 SiC 2 and accumulated at the trigonal junctions first. At higher temperature of 1100°C or prolonging the annealing time to 60min, considerable amount of Cu diffused to Ti 3 SiC 2 and filled up the grain boundaries leaving a mesh structure.