Frictional behavior of atmospheric plasma jet deposited carbon–ZnO composite coatings

The tribological behavior of carbon–zinc oxide composite coatings (Csingle bondZnO) grown on silicon substrates using an atmospheric pressure plasma jet method was evaluated by using a reciprocating pin-on-disk tribo-tester. The substrates were slid against a stainless steel ball with a diameter of 1 mm under a normal load of 20 mN. The corresponding Hertzian contact pressure was 250 MPa. The results showed that the frictional behavior and the wear resistance of the ZnO coating could be significantly improved with the addition of carbon. The improvements were attributed to higher hardness and Young’s modulus of the Csingle bondZnO coating compared to those of the ZnO coating as well as to production of a smooth carbon-rich layer on the wear track. The concentration of carbon and the amount of sp3 bonds in the carbon phase varied with deposition temperature and affected the frictional behavior. The lowest friction coefficient of 0.16 was achieved at deposition temperature of 250 °C.