A Surface Modification Method by Using EDM

It is very important to increase the hardness and abradability of tool and die surface. There are many surface modification methods now, such as Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD). However, these methods depend on special equipments and the workpiece needs pre-process. Thereby they can't be used in ordinary workshop environment easily. This paper introduces a surface modification method by using Electrical Discharge Machining (EDM). With ordinary EDM machine tool, kerosene dielectric fluid, and special powder molding electrode, a kind of hard carbide ceramic layer with great abradability and corrosion resistance can be deposited on the workpiece surface in the process of EDM. The principle and experiments of this technology are shown in this paper. Experimental results prove that the minimal hardness of the ceramic layer deposited by EDM is more than 5 times harder than that of the matrix. In the same conditions of wear test, the weight loss of the surface treated by EDM is about one seventh of the weight loss without treatment, and is about one third of the weight loss treated by PVD. This kind of carbide ceramic layer will be useful to lengthen the life of tools and dies.