Study On Electrochemical Deposition Process And Performance Of Nickel-Diamond Coating On Cemented Carbide Surface

Cemented carbide tools have good comprehensive performance,which can meet the needs of different industries.Three holes cemented carbide blade is commonly used in modern industrial production tools,often used to cut a variety of plastic films,paper,cloth,metal plate.However,with the emergence of new materials and new processes,industrial production has put forward higher requirements for cemented carbide tools.Therefore,the surface remanufacturing technology of cemented carbide urgently needs new breakthrough.Electrodeposition,as a mature and low-sedimentation process,still occupies a large proportion in modern industrial products.In this paper,a new process of electrochemical deposition of nickel-based nano diamond coating on cemented carbide blade was explored.The surface hardness and wear resistance of the coating were improved as much as possible while ensuring the adhesion of the coating.The surface of cemented carbide is different from that of ordinary steel.Due to the characteristics of its production process,the blade substrate contains a large number of micropores,and the micropores contain impurities,lubricants,ions,etc.,resulting in poor adhesion and even difficult plating during electrodeposition.Therefore,it is necessary to develop a special surface pretreatment scheme according to the characteristics of its powder metallurgy.In this paper,the cemented carbide substrate was soaked in acid-base solution,and the pretreatment process suitable for three-hole cemented carbide blade was determinsed by scratch tester.In order to ensure the uniform dispersion of nano-diamond in the plating solution,a variety of dispersants were used to verify the dispersion effect.The particle size distribution of diamond suspension was measured by particle size distribution tester,and the selection and concentration of dispersants were finally determinsed.Single factor analysis was used to study the influence of the amount of diamond and dispersant on the hardness and surface morp Hology of the coating,respectively.The use ratio of dispersant and diamond was determinsed by orthogonal test,and the nickel-based nano diamond coating and pure nickel coating were prepared by the optimized data.Finally,the coating was rotated for 10 mins under the same load on a rotary disc friction and wear tester,and the width of the wear scar was observed by the optical microscope.In the orthogonal experiment,hardness was used as the main evaluation standard,and nine groups of experiments with three factors and three levels were arranged.The optimal experimental data were optimized by using spass software to analyze the orthogonal experiment data.Friction and wear experiments can not only obtain the friction coefficient of the coating,but also analyze the width and wear form of the wear scar,and fully judge the wear resistance of the diamond composite coating.The experimental results show that the suitable pretreatment process of cemented carbide not only increases the adhesion between the coating and the substrate,but also solves the problem of difficult deposition of cemented carbide inserts in the preparation of nickel-based nano diamond.The surface roughness of cemented carbide increases from 430 nm to 487 nm after mixed acid treatment for 10 s and Murakam solution treatment for 25 mins.When only Murakam solution was used for etching within 15 mins,the adhesion of the coating gradually increased from 23.44 N to 122.23 N.When the concentration of dispersant 5040 is 4g /L,the diamond particle size distribution is 64 nm,while the particle size distribution is 372 nm without dispersant.When the concentration of dispersant 5040 is 1g /L,the diamond particle size distribution reaches 44 nm.The selection of dispersant reduces the agglomeration of diamond in the plating solution.At the same time,it was found in the electrodeposition process that the addition of dispersant 5040 greatly reduced the agglomeration of diamond particle size in the coating.The orthogonal experimental data show that the hardness of the composite coating is proportional to the diamond particle size,and inversely proportional to the concentration of dispersant.The parameters after orthogonal optimization are diamond particle size 250 nm,diamond addition 4 g / L,dispersant addition0.5 g / L.The hardness of the composite coating can reach 860 HV,which is greatly improved compared with the pure nickel coating 500 HV.Friction and wear experiments show that the surface friction coefficient of the coating is pure with the addition of diamond particles.