Research On Key Techniques Of Electrical Discharge Coating

Electrical Discharge Machining (EDM) technology has been regarded much by the manufacturing since it came out. Now EDM is applied broadly in the machining fields such as difficult-to-machine material, complex curved face, precise surface, and low-rigidity parts. The research fields of EDM become more and more multiple by lots of hard work of scientific researchers in the world.Electrical Discharge Coating (EDC) is a new surface modification technology developed at eighty years last century in Japan. It has some advantages compared with some traditional modification methods such as PVD or CVD, for example: it doesn't need special device and can finish the modification by using the normal EDM machine in the workshop; the process of EDC is simple and it doesn't need some complex pretreatment technology of other methods.One important difference of EDC compared with EDM is that the former uses the special electrode. The mechanism of EDC is studied aiming at the special performance of the electrode. The fine TiC powders with a series of good characteristics are used as the special electrode materials. The sintering method is adopted to manufacture the special electrode. The sintering temperature must be controlled strictly to satisfy the EDC process need.The technology rule is studied form some aspects: the surface roughness changing rule of coating, the average thickness changing rule of coating, it mainly include the effect of electrical parameters, machining area and machining polarity to the coating average thickness. On the basis of studying the EDC electrode wear rule, the forming efficiency of coating is also analyzed.Microhardness, friction wear and corrosion resistant performance of the coated-workpiece are analyzed in this paper. Through the analysis of the alloy component and structure of the coated-workpiece, the changing reason of workpiece surface performance is explained soundly.The coating device for complex curved surface tool is developed according to some characters of EDM machine. Different dimension of drills and milling cutters are easily coated by this device. Through the drilling test in same drilling conditions with coated and uncoated drill, the result shows that the life of coated drill improves about one time than the uncoated drill.Because the coating surface has distinct crack by traditional EDM pulse generator, the EDC pulse generator is researched in this paper. The coating deposited by EDC pulse generator is very smooth and uniform and there are nearly no crack. And the surface roughness value by using EDC pulse generator is lower than by using EDM pulse generator and the surface roughness value is about one quarter of the value with normal polarity. The coating forming efficiency by using EDC pulse generator is about 1.8 times with normal polarity and 3.5 times with negative polarity than by using normal EDM pulse generator.