| Cemented carbide tools are widely used for high-speed and ultra-high speed machining because of their excellent properties such as high hardness and high wear resistance.With the continuous development of high speed cutting technology,it requires higher cutting performance of cemented carbide tools.The surface quality of carbide blade has become one of the key factors that restrict the accuracy and service life of high speed cutting tool.The chemical mechanical polishing technology can effectively improve the surface accuracy and cutting performance of cemented carbide tools.At present,the research on chemical mechanical polishing of cemented carbide blade is mainly focused on the cutting performance of the polishing blade,many problems about material removal mechanism and technology in the process of chemical mechanical polishing of carbide inserts have not been completely solved.However,the accuracy of the surface of the polished blade depends largely on the understanding of the mechanism and the control of the process.Therefore,in this paper,the mechanism and process of chemical mechanical polishing of YG8 cemented carbide blade are studied by combining theory and experiment.The main research work is as follows:First,a chemical mechanical material removal model considering chemical action is established based on the theory of mucosa and the principle of friction and wear.The formation process of chemical oxidation film on the surface of the blade was revealed by analyzing the chemical oxidation of YG8 carbide blade in the weak acidic hydrogen peroxide based polishing solution.By studying the actual contact area and pressure of the chemical mechanical polishing process,the contact form of the polishing pad-abrasive-blade and the grinding model of the abrasive particles,the chemical mechanical material removal model and the expression equation of the MRR are derived.The equation shows that material removal rate is mainly affected by polishing pad characteristics,abrasive characteristics and polishing speed and pressure.Then,the effect of polishing pad characteristics(material,surface roughness,surface structure),abrasive properties(material,particle size,concentration)and process parameters(polishing speed and pressure)on the processing process of YG8 blade CMP was analyzed by the test method,and the rationality of the material removal mechanism was verified.The effective polishing pad and abrasive material and the reasonable process parameter range of YG8 Blade chemical mechanical polishing were obtained.The results show that the fine canvas polishing pad has the best processing effect but short service life.The polishing effect of polyurethane polishing pad is inferior to the fine canvas,but its stability is high.The effect of alumina grinding particle polishing is the best.The reasonable parameters range is D=1μm～3μm,C=10wt%～15wt%,V= 50～70 r/min,and P=155.25～207 KPa.Finally,in order to further improve the surface quality of the blade and improve the material removal rate of YG8 Blade chemical mechanical polishing,a central composite design test with four factors and three levels is designed.The response surface method is used to optimize the material removal rate,and the prediction model between the process parameters and the surface roughness and the material removal rate is established respectively.The optimal process parameters of YG8 blade CMP process are obtained by the model:polishing speed V=65.5r/min,polishing pressure P=156.7KPa,abrasive particle diameter D=1.1μm,concentration C=13.98wt%,and the predicted material removal rate is 56.56 nm/min,and surface roughness is 0.019μm.The accuracy of the prediction model and the processing effect of the best combination of process parameters were verified. |
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