Investigations Into the Removal of EDM Recast Layer With Magnetic Abrasive Machining

Electrical Discharge Machining (EDM) is a non conventional machining process capable of accurately machining parts with high hardness and of complex shapes. The sparks produced during the EDM process cause localized melting on the work surface. The formation of recast layer is very common on EDMed surfaces. The recast layer reduces the service life of the die or mould surfaces, especially under fatigue loads. In the present work, Magnetic Abrasive Finishing (MAF) process has been explored as a method to remove the recast layer formed on a EN 31 steel cylindrical specimen machined by EDM. MAF process is one of promising methods capable of removing the material at micro/nano level under gentle mechanical forces. The diamond based sintered magnetic abrasives have been used to machine the EDMed surface. The experimental results indicate that the EDMed surface of EN-31 steel can be successfully finished with diamond sintered magnetic abrasives. On the finished surfaces, no evidence of micro cracks, voids and recast layer has been seen. Moreover, an average improvement in the surface finish up to 80% over the initial surface finish has been obtained. The micro hardness measurement on MAFed surface shows that brittle and hard layer has been removed. SEM photographs indicate the success of MAF for removal of EDMed surface.