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Low temperature vacuum deposition of tungsten carbide coatings, W1−yCy with compositions that varied from y=0 to 0.9, was investigated. Special attention was given to the production of nanocrystalline carbides with coatings of y>0.5. Previous attempts at producing WC with excess carbon at near room temperatures resulted in the formation of amorphous phases. In this study, crystalline WC was produced at 45 and 300 °C by the intersection of plasma fluxes from magnetron sputtering of tungsten and laser ablation of graphite. At both temperatures, formation of WC chemical bonding and nanocrystalline cubic β-WC1−x was observed using x-ray photoelectron spectroscopy and grazing angle x-ray diffraction when the carbon content was increased more than 30%. Increasing the substrate temperature to 300 °C did not affect the percentage of WC bonding, but it did promote considerable crystallization of cubic WC. As the carbon content was increased to more than 50%, a second phase consisting of amorphous carbon (a-C) was observed together with amorphitization of β-WC1−x. The a-C phase was identified as amorphous diamond-like carbon (DLC) by Raman spectroscopy. At 60–80 at. % C, a two phase structure was produced, which was composed of nanocrystalline β-WC1−x with 5–10 nm grains and amorphous DLC. The hardness of the WC/DLC composites was about 26 GPa based on nanoindentation tests. Correlation of the chemistry, microstructure, and mechanical properties of WC and WC/a-C coatings is discussed.

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