Study On Surface Roughness Of Chemical Mechanical Polishing Of Cemented Carbide Tool

Cemented carbide tools with high hardness,high wear resistance and high heat resistance have become the main tools for high-speed and ultra-high-speed machining,precision molds and tools in China.The use of chemical mechanical polishing to machine the surface of the carbide tool allows the tool's rake face to be smooth and flat with less surface damage,which improves tool durability and improves cutting performance.In the chemical mechanical polishing of cemented carbide tools,surface roughness is an important criterion for judging the surface quality of the tool.Establishing the surface roughness theoretical model of cemented carbide tools is beneficial to choosing reasonable polishing parameters,ensuring the quality of tool polishing and improving the efficiency of tool production.Based on the contact form among the abrasive grains,the tools and the polishing pads,combined with the mathematical expectation in Mathematical Statistics and the definition of surface roughness in Tribological Principles,a theoretical model of surface roughness of cemented carbide tools has been established.The main research contents are as follows:?1?The surface roughness theoretical model of chemical mechanical polishing of cemented carbide tools is studied.By analyzing the mechanical properties and moving form of the polishing pad and the tool,the contact model among the tool,the abrasive particles and the polishing pad has been established.The theoretical calculation of the effective number of abrasive grains and the depth of the abrasive grains pressed into the tool surface has been carried out.It is considered that the polishing pressure,the abrasive concentration and the abrasive particle size affect the depth at which the abrasive grains are pressed into the tool surface.According to the Rayleigh distribution of the workpiece depth of the abrasive grain cutting,combined with the mathematical expectation in the Mathematical Statistics and the definition of the surface roughness in the Tribological Principle,the theoretical model of the surface roughness of the cemented carbide tool has been established.The theoretical model shows that the tool surface roughness value is inversely proportional to the abrasive concentration C_m,proportional to the abrasive particle size D_m,and also proportional to the polishing pressure P^1/3 power.?2?The theoretical model of tool surface roughness based on alumina abrasive polishing was studied.The effects of six different kinds of abrasives on the surface of cemented carbide tools have been analyzed by experiments.The experimental results show that the lowest surface roughness can be obtained by polishing with diamond abrasives,followed by alumina abrasives.Considering the high production cost of diamond abrasives,alumina abrasives can be used in the machining of carbide tools.Considering the influence of the type of abrasive properties and the chemical action of the polishing solution on the surface roughness of the cemented carbide tool.The correction coefficient K_cm of the surface roughness theoretical model of the cemented carbide tool has been introduced.The theoretical model correction coefficient K_cm is obtained by three-factor two-level experimental fitting of alumina abrasive.Finally,A theoretical model of the surface roughness of the tool based on alumina abrasive polishing was established.?3?The effects of the abrasive concentration,the polishing pressure and the abrasive particle size on the surface roughness of YG8 cemented carbide tools have been investigated by single factor experiments.According to the experimental results in the range of the abrasive grain size D_m 3?m to 10?m,the abrasive grain concentration C_m 7.5 wt%to15.0 wt%,and the polishing pressure P 48.48 kPa to 96.96 kPa,it is concluded that the surface roughness value changes with the polishing parameters are consistent with the results of theoretical model prediction.The relative error between the experimental and theoretical values of surface roughness tends to be stable,and the average relative error is stable at around 30%.It is proved that the tool surface roughness correction model has certain effectiveness.The above research results show that the theoretical model of tool surface roughness based on alumina abrasive polishing has certain guiding significance for the selection of chemical mechanical polishing process parameters of cemented carbide tools.