Preparation And Study Of WC-Co Cemented Carbide Wear Resistant Coating With Graphite Addition

Carbide coatings are widely used in the preparation and use of wear resistant coatings due to their high hardness and good red hardness.WC-Co cemented carbide wear resistant coatings are typically prepared by a spray coating process to improve the wear resistance of the substrate and to repair damaged materials.However,decarburization occurs during the WC-Co cemented carbide coating process prepared by Air Plasma Thermal Spray?APTS or APS?to increase the porosity of the coating.In this study,WC-Co cemented carbide and graphite solid lubricant with good hardness and wear resistance were used as the original powder.The graphite/WC-Co hard alloy wear-resistant coating was prepared on the surface of M35 high-speed steel by APS process.The effects of APS spraying process parameters,mechanical milling time,graphite addition and subsequent high-current pulsed electron beam surface modification on the microstructure and properties of the coating.Scanning electron microscopy?SEM?,energy dispersive spectroscopy?EDS?,X-ray diffraction?XRD?were used to investigate the microstructure and phase composition of the coating,using Image J,Vickers hardness tester,friction and wear tester,high precision balance,The coating adhesion automatic scratching device explores the properties of coating porosity,microhardness,friction coefficient,grinding loss weight and bonding strength.The following conclusions were obtained:?1?APS optimal process parameters 600A,voltage 40V.Under this parameter,the powder coating effect is good,the coating is dense,the porosity is low?about 12.1%?,the coating has high microhardness?about 526 HV?,and the interface bonding strength is high?about 80.465N?.The coating has a low coefficient of friction?approximately 0.5?.?2?The graphite/hard alloy core-shell structure spray powder was prepared by mechanical ball milling method.It was found by powder observation and spray coating.The structure of the coating prepared by spraying was the best when the ball milling was mixed for 16 hours and the graphite addition amount was 6%.The coating has a thickness of 200-300?m,a porosity of 6.5%,a microhardness of 600 HV,and a stable friction coefficient of 0.1 h.The phase components present in the coating are mainly Co₃W₉C₄,WC,W₂C and the like.Co₃W₉C₄ is a hard phase with good toughness,which can improve the microhardness of the coating.The addition of graphite to 6%of the coating has the least W₂C phase and the lowest degree of decarburization,indicating that the coating of graphite on the hard alloy has alleviated the decarburization.Effect.Graphite and cemented carbide composite lubricating films were observed on the surface of the coating during friction and wear,providing continuous lubrication during coating wear and reducing the friction coefficient of the coating.?3?The spray coating is remelted by a high current pulsed electron beam?HCPEB?irradiation.A modified thickness of about 300?m was observed and the coating was dense.The microhardness is about 800 HV,and the stable friction coefficient is 0.06 at 1 hour.Microstructure observation showed that the surface of the coating was transformed into nanocomposite structure,and WC-Co was transformed into nano-scale Co₃W₉C₄ and WCx structure?about 100 nm?.The graphite portion was melted,the corners were rounded,and the size was about 10?m.At the same time,graphene,diamond and other tissues are formed on the surface,and their presence promotes the improvement of microhardness and wear resistance.Typical modified structures such as craters and microcracks appear on the surface of HCPEB,and the pores and gaps on the surface of the original coating are melted and filled.