Improving the mechanical and tribological properties of TiB2/a-C nanomultilayers by structural optimization

A novel nanomultilayered architecture was developed through magnetron sputtering to simultaneously achieve excellent mechanical and tribological properties in TiB2/a-C film. Structural optimization was conducted by adjusting the modulation period from 1 to 10.5 nm. Film hardness and toughness were significantly improved and reached the optimal value at Lambda = 6.6 nm. Combination of a sufficient number of heterointerfaces and appropriate individual layer thickness played a key role in hardening and toughening. The internal stress increased linearly with the increase in modulation period, which may be related to the reduction in the number of interfaces. Furthermore, a low friction coefficient of about 0.1 was achieved in the steady state at Lambda <= 6.6 nm due to the formation of a uniform and compact transfer film on the worn ball surface. The improved mechanical performance and the presence of an effective transfer film resulted in an outstanding anti-wear performance at Lambda = 6.6 nm.