Study On The Approach To Improve The Adhesion Of Diamond Coated Milling Cuters And Its Performance

In the field of processing graphite electrode,the cemented tungsten carbide?WC-Co?milling cutter has serious wear in high-speed milling,but diamond coated milling cutter has obvious advantages in wear resistance.To guarantee the processing quality and service life of diamond coated milling cutter,first the adhesion is needed to enhance,secondly improving the crystalline quality and wear resistance should be focused.In this paper,hot filament chemical vapour deposition?HFCVD?was used to make diamond film,the effects of different pretreatments on the adhesion of diamond films were studied including sandblasting,chemical etching and interlayer coating.The deposition parameters of making superfine-crystalline diamond film with low friction coefficient and great wear resistance were studied based on high adhesion,then superfine-crystalline diamond coated milling cutter with high adhesion was prepared to study its performance and service life of high-speed milling graphite compared to cemented tungsten carbide milling cutter without coating.The microstructure,morphology,adhesion and properties of the samples were characterized by a variety of methods including scanning electron microscope,X-ray diffraction,Raman spectrometer,3D surface topography analyzer,ultra-depth microscope,friction and wear test instrument,Rockwell hardness tester and so on.The main research work and conclusions are as follows:?1?Sandblasting orthogonal test was adopted to obtain the sandblasting pretreatment parameters with the best adhesion of diamond film,and the step of Murakimi reagent etching was necessary through the results,the mechanical interlocking force between the diamond grain and the matrix could be enhanced by the sandblasting pretreatment,and the alkali treatment could increase the depth of removing Co by acid etching.The composite pretreatment of optimized sandblasting process plus two-step chemical etching could not only improve the nucleation density and uniformity of diamond,but also solve the problem of the agglomeration of diamond grains effectively.The growth speed and surface quality of diamond film were improved,and the adhesion of diamond film was raised to HF1 level.?2?Cr,WC,AlCrN,Cr/WC and Ti/WC interlayers were prepared with the thickness of600 nm,500 nm,2?m,1.4?m and 600 nm respectively.The diamond nucleation density of Cr interlayer was 5.2×10⁸ cm^-2,and the adhesion of diamond film was improved a bit,reaching HF3 level,but other four interlayers could not contribute much to the adhesion of diamond films,especially Ti/WC interlayer had the worst effect on suppressing the diffusion of Co.?3?The process parameters of depositing superfine diamond films were investigated,methane,argon and hydrogen gas were adopted as source materials,the grain size and roughness of diamond decreased when the concentration of Ar was increased from 70%to90%.When the concentration of Ar was 90%,the diamond film had the minimum average grain size of 300 nm,the lowest surface roughness of 90 nm,and the best wear resistance.?4?The superfine diamond coated milling cutter was prepared,and its performance of high speed milling graphite was tested compared to cemented tungsten carbide milling cutter without coating.It showed that the service life of diamond coated milling cutter was increased by 67%compared to cemented tungsten carbide milling cutter without coating.