Research On Graphene As The Lubricative Additive In Metal Cutting Fluid

Metal cutting fluids are mainly divided into water-soluble and oily metal cutting fluid.Water-soluble lubricants has become a major thrust of research of the metal cutting fluid because of its inexpensive,environmentally friendly,and good cooling effects.But the water-soluble metal cutting fluids exhibited poor lubricity,therefore,study on the lubricating additive are becoming the hotspot of research.In recent years,carbon nanomaterials,such as graphene,have been investigated as the water lubricity additives and presented good tribological properties.However,most of these materials are hydrophobic and cannot be dissolved or dispersed in water.Therefore,these must be subjected to hydrophilic or lipophilic treatment so that can be used as the corresponding water-based lubricant additive or oily lubricant additive.In this paper,the changes of lubricity of different graphene,and its effects on the lubricity of the metal cutting fluids were studied.The graphene was subjected to lipophilic and hydrophilic treatment;and their effects on the lubricity of oil-based metal cutting fluids and water-soluble metal cutting fluids were also studied.The characterization and analysis were performed by tapping torque,Fourier Transform Infrared Spectrometer(FT-IR),Thermogravimetry analysis(TGA),X-ray Diffraction Analysis(XRD),,and Atomic Force Microscope(AFM).The main contents of this paper are as followed::(1)Different sizes of graphite graphene sheets were prepared by using different graphite powders as raw materials.Different levels of oxidants were used to prepare different thickness ofthe oxide plate graphene.Oxidized graphene with different reduction degree were prepared to study the effects of the geometrical structure and the degree of oxidation(ie,transverse dimension and thickness)on the graphene oxide plate(GOP)and the degree of oxidation on the lubricating properties of the metal cutting fluid.Different size and different reduction degree of graphene oxide were prepared,and the lubricity of the aqueous solution of graphene oxide was better than that of pure water,but was worse than that of water-based metal cutting fluid in the market.However,the water-soluble metal cutting fluid treated with graphene oxide presented some but not obvious improvement on the lubrication property.And the lubricity of the graphene oxide was increased with the decreases of the lateral dimension of the graphene oxide.(2)The graphene oxide was modified with the octadecylamine by covalent bonding method,and the effects of modified graphene oxide on the lubricity of the oily metal cutting fluid were investigated.The results show that the octadecylamine was successfully modified on the surface of graphene oxide by covalent bonding,and present a good dispersibility in the oily metal cutting fluids.The oily metal cutting fluid added octadecylamine modified oxidized graphene exhibited just a little enhance on the lubrication,but the lubrication is not obvious.(3)The graphene oxide was modified with the polyvinylpyrrolidone(PVP)by noncovalent bonding method,and the effects of PVP-modified graphene oxide on the lubricity of the water-soluble metal cutting fluid were investigated.The results show that the PVP was successfully modified on the surfece of graphene oxide by noncovalent bonding,and exhibited a better dispersibility in the water-soluble metal cutting fluids.The water-soluble metal cutting fluid added PVP modified oxidized graphene also exhibited some but not obvious improvement on its lubricity.