Influence of Ti addition on the properties of W–Ti–C/N sputtered films

Thin films of W–Ti–C/N were deposited by d.c. reactive magnetron sputtering from W–Ti targets with 0, 10, 20 and 30 wt.%Ti. The influence of titanium and interstitial element (carbon and nitrogen) contents on the structure, hardness and adhesion of the coatings was evaluated by X-ray diffraction analysis, ultramicroindentation and scratch-testing, respectively. The results show different compositional dependencies of the structure and grain size of the films. Hardness was related with the structure of the films, including lattice distortion and grain size. The higher hardness values (≈50 GPa) were obtained for W–Ti–N films with 40–45 at.%N deposited from the W–20 wt.%Ti target in a reactive N2 atmosphere. However, these films present relatively low adhesion to the substrates with critical loads of 30 N. The best compromise between hardness and adhesion was reached for W–Ti–N films with low nitrogen and titanium contents.