On the Efficacy of IF–WS₂ Nanoparticles as Solid Lubricant: The Effect of the Loading Scheme

Fullerene-like WS₂ (MoS₂) nanoparticles (IF) have been studied in the past as solid lubricants. Using the tribological ball-on-flat experiments, it was shown that the size of the aggregates and their distribution determine the penetration and entrapping of the IF nanoparticles at the interface. It is expected that the wedge clearance at the inlet of the contact, i.e., the oblique-angle entrance to the contact zone between the two mating tribological surfaces, as well as the average surface roughness, can limit the supply of the lubricant into the interface in, e.g., the block-on-ring experiment. In the present series of experiments, the Stribeck curve was designed first using a linear loading scheme and pure oil. It was concluded that a wedge clearance (oblique-angle) in the inlet of the contact zone leads to entrapment of the IF nanoparticles and their compaction, which hamper the supply of the fluid lubricant into the interface. A ball-on-flat and flat block-on-ring friction devices with wedge clearance in the inlet of the contact can distort the efficacy of IF. Procedures for improving the supply of the IF nanoparticles to the contact zone and improving thereby their efficacy are considered.