Experimental Research On The EDM Electrode Manufactured By Pulse Electroforming Ni-Al₂O₃ Composite Materials Based On Ultrasonic

EDM is one method that producing local instantaneous high temperature to gradually removal of the metallc material by continually pulsed spark discharge between the workpiece and the tool electrode. The workpiece and the tool electrode in the EDM are all subject to the impaction of charged ions, electrical erosion product and high melting temperature, both of them will have loss. When EDM machining such a complicated cavity or a deep hole with a smaller diameter, the loss of the tool electrode will particularly serious. With the increase of electrode machining depth, the machining speed will gradually reduce and the material removal rate will decrease. In severe cases, the processing can not continue, and it can not obtain a good machining precision. Therefore,how to improve the anti-corrosion properties of EDM electrode material has become a key to extend the electrode’s life, improve the accuracy and repeatability of the workpiece shape.In order to explore the processes and methods to improve the performance of anti-electrical erosion of the EDM electrode material, in this dissertation, Ni–Al₂O₃composite deposits and Ni have been plated to the outer surface of the copper electrode,forming a composite coating. the influence of various factors on Al₂O₃ particle content in the composite coating and its microhardness have been studied, these factors including ultrasonic power, the addition amount of the particles, the average current density, bath temperature and pulse duty, and detecting the composite coating’s corrosion resistance and surface roughness, focused on the comparative study of the Electrical Erosion Resistance of the composite electrode, nickel electrode and copper electrode by EDM machining test.The hole that processing out by the copper-plating Ni-Al₂O₃ composite electrode has a better surface roughness and the conicity reduced accordingly, the loss of the composite electrode decreased significantly compared to the copper electrode. The main works completed and conclusions were presented as follows:1. Determine the formulations of the plating solution, the content of Al₂O₃ in the composite plating layer was set to the measuring indicators. Developed the Pulse Electroforming Plating process scheme by orthogonal test method. The greater impact of process parameters on the co-deposition amount of Al₂O₃ in the composite coating were performed Orthogonal Test, they are addition amount of Al₂O₃ particles, plating solution temperature, cathode current density, duty cycle and ultrasonic power. Preliminary results the optimum process parameters to prepare the Ni-Al₂O₃ composite, compare all theprocess parameters to obtain a significant effect sequence on the Al₂O₃ content in composite plating layer: Ultrasonic power> Cathode current density> The amount of Al₂O₃ in the plating solution> Duty cycle> Bath temperature. Analysis of each composite coating’s performance in the orthogonal experimental groups.2. Set the main factors affecting the composite electrode electrically anti-corrosion properties as an index, including the content of Al₂O₃ in the composite coating and composite coating’s hardness. Optimized by single factor test to determine the ultrasound-Pulse Plating Preparation of Ni-Al₂O₃ composite electrode’s optimal parameters: the amount of Al₂O₃ in the plating solution is 30 g/L, the plating solution’s temperature is 50℃,cathode’s average current density is 3 A/dm2, the duty cycle is 0.3, ultrasonic power is40 W.3. Making EDM hole’s comparison tests between the composite electrodes under eight different preparation conditions with the copper electrode, the strength of anti-electric erosion resistance were comparative studied among copper electrode, nickel electrode and Ni-Al₂O₃ composite electrode, and compared the machined hole’s conicity size. The results showed that: plating Ni-Al₂O₃ composite electrode with ultrasonic agitation and pulse power have the best anti-electrolytic corrosion resistance and hole’s conicity.