Research On Force-induced Rheological Polishing Slurry Based On Material Characteristics Of Cemented Carbide

Cemented carbide has excellent comprehensive mechanical properties and has been widely used as tool material.Coated cemented carbide tool polishes its surface before coating to enhance the bond between coating and matrix.Due to high hardness and wear resistance of cemented carbide,it is difficult to polish,especially for the polishing of complex cutting edges such as thread chaser.The traditional brush polishing method is easy to cause tool edge collapse,chipping.Force-induced rheological polishing utilizes the shear thickening properties of non-Newtonian fluids to form a"flexible fixed abrasive tool"in the contact area between polishing slurry and workpiece,realizing the efficient polishing of workpiece surface.At the same time,the fluidity of the polishing slurry ensures the polishing requirements for complex shaped tools.Polishing slurry is one of the most critical factors in force-induced rheological polishing.In order to improve the polishing performance of force-induced rheological polishing slurry,in this paper,polishing slurry is developed based on the material characteristics of cemented carbide.The main research contents are as follows:The material characteristics of cemented carbide tool were studied.The average Vickers hardness of cemented carbide was 1634.31 HV by microindentation test.The metallurgical corrosion test of cemented carbide was carried out by using the Murakami reagent.The microstructure of cemented carbide tool was observed,and the energy spectrum analysis showed that the cemented carbide was mainly composed of four elements:C,O,Co and W,the contents were 8.14 wt.%,0.43 wt.%,4.17 wt.%and 87.25 wt.%,respectively.The experimental results clarify the basis for the determination of the composition of basic force-induced rheological polishing slurry and the selection of chemical synergists.In order to solve the problem that the aqueous solution of multi-hydroxyl polymer solid particles in basic force-induced rheological polishing slurry cannot be preserved for a long time,the antiseptic research of polishing slurry was carried out.The antiseptic effect of four kinds of antiseptics at different concentrations was analyzed by observing the inhibition effect of bacterial colonies in polishing slurry.The results show that the addition of 0.10 wt.%modulated antiseptic A can effectively solve the antiseptic problem of polishing slurry.Aiming at the problem that the solid particles and abrasives in polishing slurry are easy to settle,the anti-settling effect of the three anti-settling agents on particles in the polishing slurry was studied by observing the stratification phenomenon of the stationary polishing slurry.The results show that the solid particles and abrasives in the polishing slurry with 0.04 wt.%anti-settling agent A can still be uniformly dispersed after 15 days'stationary,which meets the requirements of the force-induced rheological polishing slurry.The polishing effect of the basic force-induced rheological polishing slurry on the complex shape cemented carbide tool was studied.The influence of polishing speed,abrasive concentration,abrasive size and inclination angle of fixture on the surface roughness of cemented carbide insert were analyzed by orthogonal experiment.The optimal processing parameter combination for force-induced rheological polishing of cemented carbide insert were obtained:polishing speed of 90 rpm,abrasive concentration of 9 wt.%,abrasive size of#8000,and inclination angle of 4°.Under the optimal processing parameter combination,the surface roughness of cemented carbide insert at the left cutting edge P_A was reduced from 121.8 nm to 7.1nm after 15 minutes'polishing.The results show that the force-induced rheological polishing slurry can realize the polishing of complex shape tool.In order to further improve the polishing efficiency of polishing slurry,the chemical synergists for cemented carbide were studied.The effects of chemical polishing slurry pH,H₂O₂ and Fenton's reagent on the polishing of cemented carbide were analyzed by single factor chemical mechanical polishing experiments.The results show that the material removal rate of cemented carbide was 17.0 nm/min,and the surface roughness was 19.6 nm at pH 3.0.With the increase of H₂O₂ concentration,the material removal rate of cemented carbide increases,and the surface roughness changes little.When the concentration of H₂O₂ was 0.5 wt.%,the material removal rate of cemented carbide was 48.8 nm/min,and the surface roughness was 14.5 nm.With the increase of Fenton's reagent concentration,the material removal rate of cemented carbide decreases,and the surface roughness increases.When the concentration of H₂O₂ was 0.5 wt.%,the concentration of FeSO₄ was 1.0 wt.%,the material removal rate of cemented carbide was 25.2 nm/min,and the surface roughness was 28.1 nm.Based on the above research results,chemical synergists were added to the basic force-induced rheological polishing slurry to prepare the cemented carbide chemical-assisted force-induced rheological polishing slurry.The effects of polishing slurry pH,H₂O₂ and Fenton's reagent on the polishing of cemented carbide were analyzed.With the increase of H₂O₂ concentration,the material removal rate of cemented carbide decreases slightly,and the surface roughness changes little.When the concentration of H₂O₂ was 0.1 wt.%,the material removal rate of cemented carbide was 15.4 nm/min,and the surface roughness was 5.9 nm.With the increase of Fenton's reagent concentration,the material removal rate of cemented carbide increases,and the surface roughness changes little.When the concentration of H₂O₂was 0.1 wt.%,and the FeSO₄ concentration was 0.4 wt.%,the material removal rate of cemented carbide was 56.7 nm/min,and the surface roughness was 5.6 nm,which is significantly better than the polishing effect of basic force-induced rheological polishing slurry?the material removal rate was 15.6 nm/min,the surface roughness was 6.1 nm?.It can be seen that the force-induced rheological polishing slurry with Fenton's reagent can achieve high efficiency and high surface quality polishing of complex shape cemented carbide tools.