Transfer Film in a Friction Contact in the Nanocomposite WC-C Coatings

The studied nanocomposite PECVD WC-C coatings exhibit coefficient of friction (COF) in the range 0.1 – 0.2 or 0.6 - 0.9 at RT. At 450°C, rough friction behavior and COF in the range 0.6 - 0.9 were obtained. The analysis of possible friction mechanisms suggests high COFs result from coating damage, abrasion by WC debris ploughing, plastic deformation and enhanced frictional heating causing localized oxidation. At 450 o C, enhanced oxidation of Fe and W leads to the formation of a transfer film in friction contact which is periodically removed and restored. Nonhydrogenated WC-C coatings tend to have higher nanohardness and indentation modulus but also higher COF than, hydrogenated coatings. PF QNM mode was successfully applied for qualitative mapping of the elastic modulus in the coatings with high stiffness.