Experimental Investigations and Analysis of Electrical Discharge Machining Of Hardened EN31 Steel Using Cermet Tool Tip

Abstract

Nowadays, alloys with high strength at elevated temperature and hardened steels are extensively used. Traditional machining processes are not capable of machining these materials efficiently. Electric Discharge machining (EDM) is one of the advanced machining processes, where the intricate profiles on hard to cut materials with greater dimensional precision can be performed. In this process, repeated electric discharges between tool and work piece are used to remove material in the presence of dielectric. EDM can machine all materials which are electrically conductive, regardless the workpiece hardness. The EDM tool does not touch the work material directly, consequently eliminating complications of vibration, chatter and mechanical stresses during machining. The EDM process is also coupled with some challenges. The tool wear problem is very critical since the tool shape degeneration directly affects the final shape of the die cavity. In most EDM operations, the contribution of tool cost to the total operation cost is more than 70%. During the cut by EDM, the material removal rate (MRR) decreases due to process instability and change of metallurgic constituent in the machining zone. The surface machined with EDM occasionally has characteristics like debris globules, cracks, craters, pores and pockmarks. Creation of recast layer or white layer and surface cracks, surface roughness, residual stress and metallurgical changes of base material is used to characterize the surface integrity. In this work, an attempt has been made to overcome the problem of tool wear in the EDM process. To reduce electrode wear, the fabrication of modified tool, having altered mechanical, electrical and thermal properties, is suggested. Materials having high melting point and wear resistance properties, with good electrical and thermal conductivity are used to reduce the electrode wear of copper based electrodes.