Study On Cooling And Lubrication Mechanism Of Magnetic Field-Assisted Fe₃O₄@CNTs Nanofluid In Micro-textured Tool Cutting

The lack of lubrication and thermal conductivity between the tool-chip interface is the key problem in the current cutting field.Micro-texturing on the rake face of the tool is an important means to improve tool wear resistance and reduce cutting temperature.Microtexturing on the rake face of the tool is an important means to improve the wear resistance of the tool and reduce the cutting temperature.However,for processing titanium alloys with low thermal conductivity and high chemical activity,it is difficult to effectively reduce the temperature of the tool-chip contact area by using only micro-textured tools.Therefore,this paper proposes to combine a microtextured tool with a nanofluid with high thermal conductivity to prepare Fe3O4-modified carbon nanotube(Fe3O4@CNTs)nanoparticles by a"co-precipitation method”.The cooling and lubricating mechanism of Fe3O4@CNTs nanofluid on the micro-textured tool in the process of cutting titanium alloy under the action of magnetic field was explored.The main research contents are as follows:First,Fe3O4@CNTs composite nanoparticles were prepared by "co-precipitation method" and the surfactant with the best mass ratio of the nanoparticles was screened out.TEM images show that Fe3O4 nanoparticles are uniformly attached to the surface of carbon nanotubes,showing better dispersion than pure carbon nanotubes and pure Fe3O4.The XRD patterns show that Fe3O4@CNTs has both the characteristic peaks of carbon nanotubes and Fe3O4,and the characteristic peak intensity at 2θ=26.3° is significantly lower than that of pure carbon nanotubes,which just proves that Fe3O4 is introduced into the surface of carbon nanotubes.The XPS spectra showed that Fe3O4@CNTs contained three elements,C,O,and Fe,and proved that the particles supported on CNTs were Fe3O4.The VSM spectra show that the magnetic hysteresis loop of Fe3O4@CNTs is S-shaped,the magnetic saturation intensity is 30.52 emu/g,the remanence and coercivity are 0,and it is superparamagnetic.The stability is best when the mass ratio of Fe3O4@CNTs nanoparticles to surfactant CTAB is 5:1.Compared with Fe3O4 nanofluids,the thermal conductivity and viscosity of Fe3O4@CNTs nanofluids are improved to a certain extent,which has a certain potential in improving the tribological properties of lubricants.Secondly,a grooved microtexture was fabricated on the surface of a TiC-based cermet tool by laser,and Fe3O4@CNTs and pure Fe3O4 nanofluids with different volume fractions were prepared as lubricating fluids for contact angle test and friction and wear test.The results show that the smallest contact angle measured between Fe3O4@CNTs nanofluid with a volume fraction of 0.5%and the textured tool is 39.1°,showing the best surface wetting performance.Under a 5 N load,the COF and Ti6Al4V wear rates of the TFC-0.5 sample were reduced by 43.9%and 59.1%,respectively,compared with the WCF.In the SEM and XPS characterization of the worn surface,the adhesion and oxidation degree of the nanofluid to the textured samples was lower than that of the conventional samples.Among them,Fe3O4@CNTs nanofluid with 0.5%volume fraction exhibited the best wear resistance on the textured substrate surface.Fe3O4@CNTs nanofluid has good wettability and thermal conductivity on the textured surface,which can promote the formation of a lubricating film at the friction contact interface,increase the heat propagation length,effectively reduce the COF,and improve the wear resistance.Finally,the effects of different magnetic field strengths on the cutting performance of textured TiC-based cermet tools under the lubrication condition of Fe3O4@CNTs nanofluid were investigated through the machining experiments of Ti6Al4V alloy.The results show that with the increase of the magnetic field strength,the cutting performance of the tool also increases.In particular,when the magnetic field strength is 1200 GS,the cutting force,surface roughness and cutting temperature are the lowest under the machining condition of TTC+FC-0.5.At the same time,compared with Fe3O4,Fe3O4@CNTs nanofluid can more effectively reduce the adhesive wear of the tool,reduce the temperature of the cutting area,and reduce the oxidation of the workpiece material.And with the introduction of microtexture and magnetic field,the surface quality is significantly improved.Compared with TC+F-0.5,the tool flank under TTC+FC-0.5 machining conditions has almost no chipping and adhesive wear,the back of the chip is smoother,and there is almost no adhesion of grinding chips and other impurities,and the layer on the front side of the chip The structure is also more compact and regular.In addition,the cooling and lubrication mechanism of Fe3O4@CNTs nanofluid on microtextured tools under magnetic field is also revealed.