Tribological investigation of WC/C coating under dry sliding conditions

Abstract

► WC/C coating had good anti-adhesion properties in sliding contact with titanium. ► Low chemical affinity and graphite transfer film resulted in good anti-adhesion. ► Wear mechanisms of WC/C coating: plastic deformation, oxidative wear, delamination. ► Delamination of WC/C coating was originated from pitting defects. Sliding wear tests of the WC/C coating against pure titanium and Si 3 N 4 balls were performed in dry ball-on-flat reciprocating (bidirectional) and ball-on-disc (unidirectional) configurations. Optical microscope (OM), profilometer, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) were used to analyze the tribological behaviour, anti-adhesion properties and wear mechanisms of the coating. The results showed that the WC/C coating exhibited mild wear and good anti-adhesion properties in sliding contact with pure titanium, which can be attributed to the coating's low chemical affinity for titanium material and the protective graphite transfer film formed on the counterpart. The WC/C coating is potential candidate in the fields of the tribological applications related to titanium material which usually has poor tribological characteristics because of the adhesion. The main wear mechanisms of the WC/C coating sliding against Si 3 N 4 were a combination of plastic deformation and oxidative wear in reciprocating sliding condition, while a combination of delamination and oxidative wear in ball-on-disc configuration. The delamination of the WC/C coating was originated from the pitting defects which formed during the coating deposition process.