Nanoparticles as Novel Lubricating Additives in a Green, Physically Based Lubrication Technology for DLC Coatings

Diamond-like carbon (DLC) coatings provide low friction and wear in the most demanding tribological contacts. However, their chemical reactivity with oil additives is poor and difficult to optimise. Moreover, even the partially effective, but high-SAPS (sulphuric ash, phosphor, sulphur) additives, will be phased out in the near future for environmental reasons. Based on recent advancements in the nanotechnology of inorganic MoS2 and WS2 nanoparticles, which lubricate through the low shear of basal planes, we propose a potential replacement of the current chemical-based lubrication with this novel, physical-based additive lubrication technology for poorly reactive DLC coatings. In our work, 30% less friction compared to steel surfaces and 50% less friction compared to the base oil was achieved by employing MoS2 nanotubes in the base oil in self-mated DLC contacts. This physical-based lubrication technology represents an innovative solution for highly effective but non-reactive surfaces and simultaneously provides green-lubrication performance.