Characterization of tribo-layer formed during sliding wear of SiC ball against nanocrystalline diamond coatings

Tribo-layer formation and frictional characteristics of the SiC ball were studied with the sliding test against nanocrystalline diamond coating under atmospheric test conditions. Unsteady friction coefficients in the range of 0.04 to 0.1 were observed during the tribo-test. Friction and wear characteristics were found to be influenced by the formation of cohesive tribo-layer (thickness ~ 1.3 μm) in the wear track of nanocrystalline diamond coating. Hardness of the tribo-layer was measured using nanoindentation technique and low hardness of ~ 1.2 GPa was observed. The presence of silicon and oxygen in the tribo-layer was noticed by the energy dispersive spectroscopy mapping and the chemical states of the silicon were analyzed using X-ray photoelectron spectroscopy. Large amount of oxygen content in the tribo-layer indicated tribo-oxidation wear mechanism.