Hard nanocomposite Ti–Cu–N films prepared by d.c. reactive magnetron co-sputtering

Two series of Ti–Cu–N films containing 0–10 at.% Cu were deposited by d.c. magnetron co-sputtering from two elemental targets in Ar–N2 gas mixture by biasing the Si (100) substrates with −150 V and +35 V, respectively. The influence of Cu content and deposition conditions were examined with regard to the microstructure, morphology, mechanical and tribological properties of these films. All films deposited on −150 V biased substrates exhibited a pronounced TiN (111) texture, while this texture was found to weaken in the films deposited on +35 V biased substrates with the addition of a small amount of Cu. Hardness enhancement from ∼22 GPa for pure TiN film to ∼30 GPa upon the addition of Cu was observed in both cases. However, in the case of −150 V bias hardness enhancement occurred in a relatively wide range of Cu content (<10 at.% Cu), whereas at +35 V bias it was only observed in a narrow range of Cu content of approximately up to 2.81 at.%. The dry friction coefficient against SUS440C steel ball decreased from high value of ∼0.8, corresponding to TiN film, to a low value of approximately 0.2 in some Ti–Cu–N films with enhanced hardness.