Tribological behavior of black phosphorus nanosheets as water-based lubrication additives

Black phosphorus (BP) with a layered structure has been used gradually as a lubrication additive in the tribological area. In this study, BP powders are produced via an easy method of high-energy ball milling using red phosphorus as a raw material. Subsequently, BP nanosheets are prepared via liquid exfoliation in N-methyl pyrolidone solvent. The tribological behavior of BP nanosheets as water-based lubrication additives (BP-WL) is evaluated under Ti6Al4V (TC4)/GCr15 contact. The results suggest that the 70 mg/L BP-WL sample exhibits excellent lubrication performance, whose coefficient of friction (COF) and ball wear rate reduced by 32.4% and 61.1%, respectively, compared with those of pure water. However, as the load increased, the tribological properties of BP-WL reduced gradually because of the agglomeration of BP nanosheets. Based on tribological experiments and worn surface analysis, boundary lubrication mechanisms are proposed. The friction reduced, which is primarily attributed to the low interlaminar shear and adsorption of BP nanosheets. In addition, a tribochemical reaction film comprising TiO₂, Al₂O₃, and Fe₂O₃ effectively protects the surface of titanium alloy/steel from wear. This new water-based lubrication additive can be used to process titanium alloys.