Research On The Process And Mechanism Of EDM Of Polycrystalline Diamond

Polycrystalline diamond(PCD)is one of the most widely used tool materials with high hardness,wear resistance and impact resistance.It is often used as a tool for machining tools,oil drills and geological drills.However,it is very difficult to process the ultra-high hardness materials with traditional machining methods.As one of the most widely used machining methods for hard and brittle materials,EDM is more suitable for processing PCD.Traditional EDM uses copper(Cu)electrodes to process PCDS,and the processing efficiency and processing quality has been poor.Graphene has excellent electrical and thermal conductivity,which can make the spark discharge more stable and uniform,and enhance the chip removal ability to improve the processing quality.Nickel can promote the graphitization of PCD.In this paper,a combination of Cu-Ni electrode and graphene dielectric is used to improve the efficiency and machining quality of PCD EDM.The main research contents and conclusions are as follows:(1)Study the effect of Cu-Ni electrode on EDM PCD and its mechanism.The effects of machining parameters and electrode materials on the surface morphology,material removal rate and surface roughness of PCD were analyzed.The results show that both electrodes achieve higher efficiency but lower surface quality when machining with high parameters.The material removal rate of Cu-Ni electrode at high parameters is 0.563mg/min,and the surface roughness is 6.25μm.At low parameters,they were 0.187mg/min and 4.96μm,respectively.At high parameters,the material removal rate of Cu-Ni electrode machining is 37% higher than that of Cu electrode machining,and the surface roughness is 2.4% lower.At low parameters,the material removal rate of Cu-Ni electrode increases by 65%,and the surface roughness decreases by 5.5%.This is due to different discharge energy processing,the removal of materials in different ways.In high parameter machining,the material removal method mainly relies on explosive force generated by high energy.The Ni atom in Cu-Ni electrode plays an auxiliary role in the graphitization of diamond.In low parameter machining,the Cu-Ni electrode mainly relies on the catalytic action of Ni atoms to accelerate the graphitization of diamond surface,and then the graphite layer with low hardness is removed by the discharge energy.(2)Study the effect of graphene powder on EDM PCD and the processing mechanism.CuNi electrode and graphene dielectric were used in EDM experiments.The results show that the machining surface is better than that in ordinary dielectric machining.The material removal rate is 87% higher than that in ordinary dielectric machining,and the surface roughness is 13% lower.The results of XRD and Raman spectra show that the graphitization degree of PCD is the highest when using graphene mixed dielectric.(3)Cu-Ni electrode and graphene dielectric were used to prepare groove microtexture on the surface of PCD by electric discharge,and the influence of surface microtexture on the tribological and wear properties of PCD was studied.Under dry friction conditions,the groove microtexture obviously improves the friction and wear performance of PCD workpiece surface,and reduces the friction coefficient of the workpiece.Under the condition of lubricating friction,the friction coefficient is lower and the friction state is better.The textured PCD workpiece has a good effect in the first half of the friction test,but the friction coefficient of the second half is greater than that of the non-textured PCD workpiece.