Surface modification process by electrical discharge machining with a Ti powder green compact electrode

This paper describes a new method of surface modification by electrical discharge machining (EDM). By using an ordinary EDM machine tool and kerosene fluid, a hard ceramic layer can be created on the workpiece surface with a Ti or other compressed powder electrode in a certain condition. This revolutionary new method is called electrical discharge coating (EDC). The process of EDC begins with electrode wear during EDM, then a kind of hard carbide is created through the chemical reaction between the worn electrode material and the carbon particles decomposed from kerosene fluid under high temperature. The carbide is piled up on a workpiece quickly and becomes a hard layer of ceramic of about 20 mum thickness in several minutes. This paper studies the principle and process of EDC systemically by using a Ti powder green compact electrode. Experiments and analyses show that a compact TiC ceramic layer can be created on the surface of the metal workpiece. The hardness of the ceramic layer is more than three times higher than that of the base body, and the hardness changes gradually from the surface to the base body. This method can find wide application in the fields of surface modification, such as the surface repairing and strengthening of cutting tools and molds. (C) 2002 Elsevier Science B.V. All rights reserved.