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The WC/a-C film prepared using a reactive magnetron sputtering system was investigated. The film structure and properties were characterized, and the friction response mechanism between this film and several counterparts was investigated under different environments. The hardness and surface roughness of the counterpart as well as the match between the properties of the counterpart and the film were identified as factors that play a critical role in the friction behaviour. The environment affected the extent of wear through physical and chemical reactions, and mechanical wear with friction chemical reactions was found to be the major mechanism of influence. This study is of great practical interest, as it will help to extend the service life of WC/a-C films and minimize loss during the initial running-in period.

The TiSiC coating was deposited on Ti6Al4V substrate material by multi-arc ion plating. Microstructures and mechanical properties of the TiSiC coating were characterized by SEM, XRD, XPS and nanoindentation. The tribological behaviors of the samples were studied in atmosphere, deionized water and seawater by tribometer. The experimental results showed that the coating exhibited a typical amorphous/nanocrystalline structure. The hardness of the TiSiC coating was up to 28 GPa, which was almost 5 times higher than that of the substrate material. The friction coefficients of the TiSiC coating decreased by 2.3%, 25.6%, 27.0%, respectively, compared with the substrate material in atmosphere, deionized water and seawater environments. The wear rates of the TiSiC coating in atmosphere, deionized water and seawater environments were about 1.72 × 10−5 mm3 N−1 m−1, 8.61 × 10−6 mm3 N−1 m−1, 6.78 × 10−6 mm3 N−1 m−1, respectively, which significantly lower than that of the substrate materials, this mainly due to the high hardness and the lubrication of graphite structure sp2C–C phase in the coating.