Effect of W content on mechanical and tribological behaviors of hard Ta1-xWxN films

Alloying with other TMs (transition metals) is an effective strategy for hardening and toughening binary TMNs (transition metal nitrides) films. In this study, Ta1-xWxN (x = 0–1) films with different W content were prepared by DC magnetron sputtering. The influences of W content on the microstructure and mechanical properties of Ta1-xWxN films were investigated. The tribological behaviors of films from room temperature (RT) to 500 °C were measured. The Ta1-xWxN films maintain a B1-NaCl structure in a range of x = 0–1. The roughness and grain size increase with raising W content. The hardness of Ta1-xWxN films reaches a maximum value of 44.2 GPa at x = 0.39. The fracture toughness (KIC) achieves 4.47 MPa·m1/2 at x = 0.57, corresponding to the higher H/E (0.158) and H3/E2 (1.06 GPa). The Ta0.24W0.76N film shows lower friction coefficient (∼0.5) and wear rates (1.5–4.1 × 10−6 mm3/N·m) from RT to 500 °C. The tribological properties of Ta1-xWxN films at room temperatures are directly relate to the H/E and H3/E2, while the tribological properties at 500 °C are mainly determined by the lubricious oxide films induced by tribo-reaction.