Basic Study On Chemical Mechanical Polishing Of Tungsten-cobalt Cemented Carbide Tool

Tool quality and performance determine the production level of manufacturing industry directly.With the rapid upgrading of China's manufacturing industry,demand for tool quality and performance is getting higher and higher in tool industry,and the important research content in the field of tool processing is how to improve tool surface quality,and then to improve tool durability.Tungsten-cobalt cemented carbide is a widely used tool material.In this paper,the basic theory of tungsten-cobalt cemented carbide tool CMP is studied,and the polishing mechanism and process influence are studied to effectively reduce the surface damage layer of the tool and improve the tool durability.The main research work and results are as follows:?1?The corrosion behavior of tungsten-cobalt cemented carbide blade in the polishing liquid is studied,and the chemical reaction mechanism of the tungsten-cobalt carbide tool CMP is disclosed.The influence of the polishing liquid pH value on blade CMP effect is studied by experiments,and it is found that when the polishing liquid pH value is 6-8,the damage layer on the blade surface is less.The chemical reaction mechanism of the tungsten-cobalt cemented carbide tool CMP is studied based on the X-ray diffraction?XRD?and the X-ray photoelectron spectroscopy?XPS?analysis,and it is found that when the blade is in the hydrogen peroxide-based polishing liquid,due to the potential difference between the tungsten carbide?WC?hard phase and the cobalt?Co?binder phase,the blade surface is prone to galvanic corrosion.The Co binder phase is corroded,producing active dissolution,and partial dissolved Co²⁺are oxidized to Co³⁺,and when it is in the air,the Co₃O₄ oxide film which is soluble in acid and easily removed by abrasive particles is formed.After the Co binder phase is corroded,it precipitates from the matrix WC,the matrix structure becomes brittle and is easily removed by the abrasive particles.?2?The influence of polishing pad and abrasive particle characteristics on tungsten-cobalt cemented carbide tool CMP is disclosed.Different characteristic polishing pads are selected to polish the YG8 cemented carbide blade.It is found that the fine canvas polishing pad can obtain the best surface quality,and the surface roughness is 0.039?m,but the service life is short and the stability is poor.It is also found that the polyurethane compound polishing pad has high durability and stable polishing performance,and the polishing effect is second only to fine canvas.Different characteristic abrasive particles are selected to polish the YG8 cemented carbide blade.It is found that the material removal rate is increased with the increase of the abrasive particle hardness,and diamond abrasive particle is the first choice for polishing YG8 cemented carbide blade,followed by alumina.?3?Material removal mechanism of tungsten-cobalt cemented carbide tool CMP is studied,and material removal rate and surface roughness theoretical models for tungsten-cobalt cemented carbide tool CMP are established.Based on contact mechanics and kinematics theory,the material removal rate model for symmetrical tungsten-cobalt cemented carbide tool CMP is established.Correction coefficient under common process conditions is obtained through experiments,and the correction model under common process conditions is established.Four important factors?polishing disk rotation speed,polishing load,abrasive particle size and abrasive particle concentration?which have a significant influence on the quality of the tungsten-cobalt cemented carbide tool CMP are selected as independent variables,and the surface roughness model of polished blade is established by Response Surface Methodology.?4?Processing technology of the tungsten-cobalt cemented carbide tool CMP is studied,and the Pareto optimal solution set of the tungsten-cobalt cemented carbide tool CMP is originally proposed.Based on the fastly non-dominated sorting genetic algorithm?NSGA-II?,the mathematical model for optimizing the polishing process parameters is established with the goal of maximizing material removal rate and minimizing surface roughness.Setting the appropriate parameters,the model is calculated to obtain the Pareto optimal solution set based on MATLAB.Five sets of process parameters are randomly selected from the above Pareto optimal solution set for experimental verification,and it is found that the relative error between experimental value and predicted value is within 10%,and the polished blade surface morphology is good.The tool durability experiment for cutting the outer circumference of1Cr18Ni9Ti for grinding and polishing tools is performed,and it is showed that the polishing tool durability is higher than that of the grinding tool.Above research results show that tungsten-cobalt cemented carbide tool CMP can effectively improve tool surface quality and reduce surface damage layer,and thereby improving tool durability.