| CVD diamond films have excellent properties such as high hardness,high thermal conductivity,low friction coefficient,high elastic modulus,good self-lubricating performance and chemical stability,and have broad application prospects in cutting tools.However,for cemented carbide diamond coating,the main factors restricting its industrialization are low adhesion strength,poor surface smoothness and difficult to guarantee machining accuracy.Therefore,it is necessary to improve the adhesion strength and surface smoothness of diamond films.In this paper,cemented carbide tools were used as the substrate.Firstly,different types of single-layer and double-layer diamond films were prepared on the surface of cemented carbide substrate by bias voltage enhanced hot filament chemical vapor deposition(BEHFCVD).The cutting performance and tribological performance of diamond composite coating film tools were studied and analyzed.Secondly,two kinds of groove micro-textures were fabricated on cemented carbide tools by laser marking machine,and boron-doped transverse groove texture(BDTAD)films and boron-doped longitudinal groove texture(BDTBD)films were prepared by BEHFCVD.Finally,the cutting test was carried out on the prepared boron-doped textured diamond film tool to study the cutting performance of the boron-doped textured diamond film tool.The main research contents can be summarized as follows :(1)Micro-diamond(MCD),nano-diamond(NCD),boron-doped micro-diamond(BDMCD),boron-doped nano-diamond(BDNCD),boron-doped micro-micro-diamond(BDM-MCD)and boron-doped micro-nano-diamond(BDM-NCD)films were prepared on the surface of cemented carbide milling cutter by BEHFCVD.The effects of grain size,crystal structure,surface roughness,surface residual stresses and substrate bonding strength of diamond films were studied.Then the cutting properties of different diamond films were studied by cutting experiments.The results show that the BDM-NCD film has low roughness,residual stress,high substrate bonding strength and good cutting performance.This is because on the one hand,the bottom boron doping can improve the bonding strength of the substrate film.On the other hand,the top-level nanoparticles have smooth surface,which effectively reduces friction.(2)Friction and wear tests of different diamond films were carried out under dry friction and water lubrication conditions.The tribological properties of diamond films were studied.The results show that the friction coefficient of diamond film under water lubrication is lower than that under dry friction.BDM-NCD film shows the lowest friction coefficient under water lubrication.It can be seen from the wear rate that the substrate adhesion strength and wear resistance of MCD film are the worst under both dry friction and water lubrication conditions,and the substrate adhesion strength and wear resistance of BDM-NCD film are the best.(3)Two kinds of groove micro-textures were prepared on the back surface of the integral carbide milling cutter by using the laser marking machine,and the boron-doped textured diamond film integral milling cutter was further prepared.Then,the cutting tests of Si Cp/Al composites were carried out by using the traditional tool(CT),boron-doped non-woven diamond(BDUTD)film,BDTAD film and BDTBD film tools.The results show that the BDTAD film has the minimum cutting force,which indicates that the reasonable position of texture can reduce the cutting force.It can be seen from the wear morphology that the wear band shape of CT tool is triangular,the cutting edge appears chipping and adhesive,and the wear amount is the largest.BDTAD film has only a small flank wear area,and there is almost no film peeling on the cutting edge,which shows that BDTAD film has the best cutting performance and tool life to slow tool flank wear.This is because the reasonable position of the texture increases the bonding strength between the diamond coating and the substrate,and improves the wear resistance of the tool.Figure 51,table 9,reference 78. |
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