Influence of nitrogen partial pressure on structure, mechanical and tribological properties of TaCN coatings

Abstract The TaCN coatings were fabricated on Ti-6Al-4V by reactive magnetron sputtering with different nitrogen partial pressures. The results show that the TaCN coatings have a columnar crystal structure of TaC, TaN nano-crystal and amorphous phases (amorphous carbon and CNx). The crystallinity of TaCN coatings decreases with the increase of N2 flow rate. It is found that hardness and adhesive strength have a downward trend and friction coefficient of TaCN coatings increases with the increase of N2 flow rate. In particular, the TaCN coating with lowest N2 flow rate of 30 sccm has the highest hardness (16.3 GPa), the biggest adhesive strength (74.8 N) and the lowest friction coefficient (~0.19). The TaCN coating exhibits an excellent tribological performances even at high temperature. The lowest friction coefficient at 400 °C could reach below 0.1 thanks to the transfer layer containing graphitic clusters which generated during friction.