Friction and wear behaviour of plasma sprayed WC–12Co coating sliding against Si3N4 under lubrication of ionic liquids

Abstract

The friction and wear behaviour of a WC–12Co coating prepared by plasma spraying sliding against a Si3N4 ceramic ball, under the lubrication of liquid paraffin and ionic liquids 1-methyl-3-butylimidazolium hexafluorophosphate and 1-methyl-3-hexylimidazolium hexafluorophosphate at room temperature, was investigated using an SRV tester. The morphology and elemental distribution of the worn coating surfaces were characterised by means of scanning electron microscopy (SEM) equipped with an energy dispersive X-ray analyser (EDXA) attachment, and the chemical state of typical elements in the boundary lubricating film on the worn coating surface was analysed by means of X-ray photoelectron spectroscopy (XPS). The SEM/EDXA analysis shows that phosphorus is uniformly distributed on the worn coating surface lubricated by ionic liquids. The XPS results also indicate that the boundary lubricating film is mainly composed of CoF2 and PFx and the tribochemical reaction products contribute to reducing the friction and wear of the plasma sprayed WC–12Co coating.