Study On Generation Mechanism And Elimination Method Of Electrical Double Layer Effect In The Process Of Electroplating CBN

Electroplating CBN grinding wheel is a kind of super hard abrasive grinding wheel, which commonly used in hardened surface gear finishing. As a grinding tool, it has the advantages of high adhesion strength and sharp abrasive morphology, which is superior to the bond grinding wheel. And the production cost is low and the service life is long also. So it heralds vast potentials for application. However, the deposition process of coating metal ions is hindered in the process of electroplating CBN grinding wheel, because of the electric double layer capacitance effect between the electrode and the electrolyte, which results the plating defects such as the bad surface quality and poor adhesion between abrasives and matrix, have limited the application and development of CBN grinding wheel. Focusing on these defects, the physical model and mathematical model of electroplating system are built, and has studied the mechanism of double layer capacitance effect. A method to eliminate the capacitance effect of electroplating double layer is proposed, and the electroplating experiment is carried out.Based on the principle of pulse electroplating and coating metal electrode-position, the effect of electric double layer capacitance produced in electroplating process is theoretically derived. The physical model and mathematical model of electroplating system are established. Physical parameters for eliminating double layer effect are determined, which respectively contains duty cycle and pulse frequency.In order to ensure the smooth implementation of the electroplating process, the influence of three kinds of anodes arrangement on electric field distribution in the process of electroplating is simulated by using finite element method. The results show that: The distribution of electric field is not uniform in the arrangement of a single anode plate with double auxiliary cylindrical anode electrodes, which is not fit for electroplating. The distribution of electric field is uniformity in the arrangement of increasing cylindrical anode electrode in the middle of anode plates, but the electric field intensity appears maximum value at auxiliary anodes in this arrangement, which may burn the plating solution. The distribution of electric field is uniform in the arrangement of double anode plates center symmetry, and the electric field intensity appears maximum value near the cathode, which is conducive to electroplating.In order to obtain the optimized parameters of pulse electroplating, electroplating experiment on 45# steel sample is carried out. And the effects of duty cycle and pulse frequency on the porosity and roughness of the plating are investigated. Research results show that: with the increasing of pulse duty cycle, the porosity of plating shows an increasing trend and the roughness of plating decreases firstly and then increases. With the increasing of pulse frequency, the porosity and roughness of plating decreases firstly and then increases. The optimized electroplating parameters combination is obtained, which is the 20% duty cycle and 0.5 k Hz pulse frequency. Based on the obtained electroplating parameters combination, single layer electroplating CBN grinding wheels are prepared, and the grinding experiments are carried out. After the narrow-deep-groove grinding on 45# steel, the abrasives on the grinding wheel are sharp, and the adhesion between abrasives and matrix is high. This proves that, the high quality single layer CBN grinding wheel can be prepared, by using the 20% duty cycle and 0.5 kHz pulse frequency electroplating parameters.