Pin-on-disk characterization of amorphous carbon films prepared by filtered cathodic vacuum arc technique

The frictional behaviour of tetrahedral amorphous carbon (ta-C) films, prepared by filtered cathodic vacuum arc (FCVA) technique, is characterized by a pin-on-disk tribometer. The influence of different test conditions, such as applied load, static sliding partners (steel, sapphire and silicon nitride balls) and test environment (nitrogen, oxygen and low/high humidity), on the frictional behaviour of ta-C films was investigated. In general, a lower average coefficient of friction was observed with increase in applied load for all the different static partners. A lower coefficient of friction was obtained when the ta-C films slid against a sapphire ball, as compared to other ball materials under the same applied load. This may be due to the interfacial film, which strongly depends on the reactive species such as oxygen, hydrogen, etc. in the surrounding with sliding partner. Ta-C films tested in an inert low humidity nitrogen environment recorded the lowest coefficient of friction. This shows the effect of tribochemical interaction of the gaseous species in the surrounding environment on the frictional behaviour of the ta-C film. The influence of different humidity on the frictional behaviour of the ta-C films was also investigated. A lower humidity leads to increased coefficient of friction.