Metal matrix solid self-lubricating materials

Thin films of wear-resistant tungsten carbide were deposited on steel substrates by sputtering of WC with magnetron sputtering in a mixed argon/acetylene atmosphere. Variation of the acetylene supply during the deposition led to the growth of the tungsten carbide films with different excesses of carbon with respect to the stoichiometric WC. Variation of bias voltage influences mainly the [C]/([C]+[W]) ratio and secondary the mechanical properties hardness and Young's modulus. The films are supposed to combine good wear-resistant properties with a low friction under dry conditions. A tribometric analysis of friction and wear shows that an excess of carbon in the hard material layer can reduce the coefficient of friction by up to 40%. However, the volume of wear increased with increasing amount of carbon, while the nanoindentation measurements revealed higher hardness and lower elastic modulus.