Controllable high adhesion and low friction coefficient in TiAlCN coatings by tuning the C/N ratio

The cutting temperature will be significantly increased while cutting high reactive titanium alloy due to the large friction coefficient of the traditional TiAlN coated tools. The tool could also easily appear adhesive wear and thereby reduce the service life. In this work, TiAlCN coatings with high adhesion and low friction coefficient were deposited by changing the C2H2 and N2 flow rates and using medium-frequency magnetron sputtering. Compared with the TiAlN coating, the hardness of the TiAlCN coating increases up to the value of 20.36 GPa, the toughness is improved by about 230%, the adhesion reaches the value of 156 N. However, the friction coefficient is only 0.231. This performance improvement is attributed to the special structure of (Ti,Al)(C,N) nano-crystalline wrapped by a C-related amorphous phase that is formed in the coating. The structure can be formed by adjusting the C/N ratio to make the C atom content exceed the solid solubility but the C/N ratio does not reach saturation. This kind of TiAlCN coating reduces the wear and inhibits the adhesive wear during the high-speed cutting process of titanium alloy. The cutting distance is also increased by 50% compared with the TiAlN coating.