Tribological properties of black phosphorus nanosheets as oil-based lubricant additives for titanium alloy-steel contacts

Macroscale Superlubricity of Black Phosphorus Quantum Dots

In the present work, Black Phosphorus Quantum Dots (BPQDs) were synthesized via sonication-assisted liquid-phase exfoliation. The average size of the BPQDs was 3.3 ± 0.85 nm. The BPQDs exhibited excellent dispersion stability in ultrapure water. Macroscale superlubricity was realized with the unmodified BPQDs on rough Si3N4/SiO2 interfaces. A minimum coefficient of friction (COF) of 0.0022 was achieved at the concentration of 0.015 wt%. In addition, the glycerol was introduced to promote the stability of the superlubricity state. The COF of the BPQDs-Glycerol aqueous solution (BGaq) was 83.75% lower than that of the Glycerol aqueous solution (Gaq). Based on the above analysis, the lubrication model was presented. The hydrogen-bonded network and silica gel layer were formed on the friction interface, which played a major role in the realization of macroscale superlubricity. In addition, the adsorption water layer could also prevent the worn surfaces from making contact with each other. Moreover, the synergistic effect between BPQDs and glycerol could significantly decrease the COF and maintain the superlubricity state. The findings theoretically support the realization of macroscale superlubricity with unmodified BPQDs as a water-based lubrication additive.

An Evaluation of the Tribological Behavior of Cutting Fluid Additives on Aluminum-Manganese Alloys

The introduction of additives enhances the friction and wear reduction properties of cutting fluids (CFs) as well as aids in improving the surface quality of the machined parts. This study examines the tribological behavior of polymer-based and phosphorus-based additives introduced into cutting fluids for the machining of Al-Mn alloys. Ball-on-disc tests were used to evaluate the coefficient of friction (COF) and lubrication failure temperature to study the performance of the additives in the cutting fluids. Surface characterization was performed on the sliding tracks induced on the Al-Mn disc surfaces and used to propose the wear and friction reduction mechanisms. The polymer-based additive possessed a higher temperature at which lubrication failure occurred, displayed comparable COF at a lower temperature under certain conditions, and possessed a steadier tribological behavior. However, the phosphorus-based additive was observed to display lower COF and wear damage from 200 °C till failure. The lower COF values for the phosphorus-based additive at 200 °C corresponded with lower surface damage on the Al-Mn surface. The phosphorus-based additive’s performance at 200 °C could be attributed to the forming of a phosphorus-rich boundary layer within the sliding wear track, resulting in less surface damage on the Al-Mn surface and lower material transfer to the counterface steel ball surface.