Electron microprobe study of deposition and diffusion of tool material in electrical discharge machining

Abstract

Electron microprobe analysis for the surface deposition and diffusion of tool material was carried out on mild steel (MS), high-carbon steel (HCS) and high-speed steel (HSS) work samples, machined by an electrical discharge process using a relaxation circuit in distilled water and kerosene at 225 and 56·25 mJ pulse energy, with copper and brass as tools. It was observed that high-energy machining results in lower surface deposition but more depth of diffusion. MS-HCS-HSS showed increasing surface deposition but decreasing depth of diffusion in the same order. Machining in distilled water at high-pulse energy resulted in lower surface deposition and depth of diffusion as compared to machining in kerosene. At low-pulse energy kerosene showed similar results. Tool material was found to deposit preferentially along the crater rims. The possibility of a certain typical geometry of crater formation in multi-spark machining is concluded. It is felt that each large crater is a result of three to four small craters, the size of which is about one-fourth of that of a large crater.