Performance and anti-wear mechanism of Cu nanoparticles as lubricating oil additives

Purpose - The purpose of this paper is to study the tribological performance and anti-wear mechanism of Cu nanoparticles as lubricating oil additives. Design/methodology/approach - An end-face wear testing apparatus is used to measure the tribological properties of Cu nanoparticles as lubricating oil additives and using a commercial SJ 15W/40 gasoline engine oil for comparison. Electrical contact resistance (ECR) is measured on a universal nano and micro tester-2 tribometer to detect the formation of tribo-film generated by Cu nanoparticulate additive. The worn steel surfaces are investigated by scanning electron microscope (SEM), energy dispersive spectra (EDS) and X-ray photoelectron spectroscopy (XPS). Findings - The results show that Cu nanoparticles used as an oil additive can improve the anti-wear and friction-reduction performance of SJ 15W/40 gasoline engine oil remarkably. The results of SEM, EDS and XPS show that a deposit film containing metallic copper can form on the worn surface, which has a film thickness of about 120 nm. Originality/value - This investigation establishes a baseline of Cu nanoparticles used as lubricating oil additives under face-to-face contact work conditions. Thus, the results are reliable and can be very useful for further applications of Cu nanoparticle additives in industry.