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.

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Porous TiO 2 films were prepared by using micro arc oxidation (MAO) in an electrolytic solution of Na 3 PO 4 with a voltage of 200 V. Three different concentrations of Na 3 PO 4 electrolyte were used, i.e. 10, 15 and 20 g L 21 . The oxidation time ranged from 5 to 15 min. The oxide films were characterised by scanning electron microscopy, energy dispersive X-ray spectrometer and X-ray diffraction. Scanning electron microscopy analysis shows that the oxide films had numerous pores with dimensions between 0 . 5 and 2 . 5 mm. The phosphorous concentrations on the surfaces of the oxide films were found to be between 4 . 73 and 5 . 73%. The anatase TiO 2 phase was determined in all the films, and no rutile phase was detected. The titanium phosphate phase was only found in the oxide films prepared with 20 g L 21 of concentration of Na 3 PO 4 electrolyte. The experimental results suggest that the low voltage MAO method is an effective way to prepare porous TiO 2 film containing a high concentration of phosphorous.

The black phosphorus (BP) powders were prepared by high-energy ball milling with red phosphorus as the raw material, and then the BP nanosheets were obtained by liquid-phase exfoliation. The tribological properties of the BP nanosheets as oil-based lubricant additives were investigated by the ball-on-disc tribometer. Results show that compared with the base oil of liquid paraffin (LP), the coefficient of friction and wear rate of the BP nanosheets as the additives in liquid paraffin (BP-LP) are lower for the same loads. BP-LP lubricants could significantly improve the load-bearing capacity of the base oil for titanium alloy-steel contacts and show excellent friction-reducing and anti-wear properties. The surface morphologies and elemental compositions of the friction pairs were further analysed using an optional microscope, scanning electron microscope and X-ray photoelectron spectroscopy. The lubrication mechanism of BP-LP can be attributed to the synergistic effects between lamellar adsorption and interlayer shear of BP nanosheets.