Preparation And Tribological Behavior Of Nano-BP/TiO₂ Lubrication Additives

Titanium alloys are widely used in aviation,aerospace,energy fields owing to superior properties such as low density,high specific strength,good corrosion resistance,etc.However,during the rolling process of titanium alloy,there are a series of problems such as large deformation resistance,serious roll wear,poor surface quality of rolled parts after processing,and easy to produce cracks,etc.Lubrication is a direct and effective way to improve surface contact states.However,due to the poor tribological characteristics of titanium alloy,traditional plastic processing lubricants can not produce efficient lubrication on titanium alloy.In view of this,this paper mainly focused on the low-cost preparation of black phosphorus(BP),studied the tribological properties of BP and BP/TiO₂ as water-based lubrication additives,revealed the mechanism of friction reduction and wear resistance,built the synergistic lubrication theoretical model,and explored the lubrication properties of water-based nanofluids in the cold rolling process of titanium alloy.BP powders were successfully prepared by high-energy ball milling method.BP nanosheets prepared by liquid exfoliation have few lamellar structures and good stability in water.The friction test results show that the BP nanosheets have excellent anti-wear properties at the concentration of 70 mg/L.Compared with pure water,the coefficient of friction(COF)and ball wear rate of BP nanosheets are reduced by 32.4%and 61.1%,respectively.The lubrication mechanism can be attributed to the lamellar adsorption of BP nanosheets,low interlaminar shear and tribochemical reaction film.BP/TiO₂ nanoparticles were successfully synthesized by hydrothermal method.It was observed that a few TiO₂ particles were attached to the surface of the BP nanosheets,and the size distribution was uniform.By orthogonal experiment,compared with pure water,the average COF of BP and TiO₂ water-based lubrication additives decreased by13.2%and 15.3%,respectively,while the average COF of BP/TiO₂ composite lubrication additives decreased by 24.5%,and the wear rate of ball decreased by 59.5%.The synergistic lubrication mechanism can be attributed to the low interlaminar shear of BP nanosheets,the self-healing effect of the ball bearing effect of TiO₂ nanoparticles,the adsorption film and the tribochemical reaction film.On the basis of the above research,the different water-based lubrication additives were prepared into water-based nanofluids for the rolling of titanium alloy sheet.The rolling test results show that the rolling force under all lubrication conditions increases successively with the increase of rolling passes.In the first pass,the rolling force under BP/TiO₂ composite water-based nanofluid lubrication decreased by 17.5%and 10.8%compared with that under no lubrication and base liquid lubrication.The surface roughness of cold-rolled titanium alloy sheet is 0.435?m,which decreases by 32.2%and26.1%,respectively,compared with that of no lubrication and base liquid.The wear mechanism in the rolling process is mainly that the lubrication film formed on the friction surface between the roller and the metal by BP/TiO₂ nanoparticles.It could greatly discrease friction and improve the lubrication performance in the rolling process,effectively improves the surface quality of the titanium alloy sheet.