Some studies on realizing the potential of abrasive electro discharge machining by metal powder abrasive additions in dielectric fluid

Abstract

Electrical discharge machining (EDM) is one of the earliest and most popular newlinenontraditional machining processes which involve removal of material through action of newlineelectrical discharges of short duration and high current density between tool electrode and the newlinework piece. It is used to machine intricate shapes even in difficult to machine materials such as newlinemetal matrix composites, super alloys and engineering ceramics with high precision. This newlineprocess is being used extensively in press tools and dies, aerospace, automotive and surgical newlinecomponents manufacturing industries. The conventional machining applied to these materials newlinetypically result in low matrial removal rates, poor surface finsh, surface damage and rapid wear newlineof the tool electrodes. newlineGeneral appearance of machined surface with conventional EDM is matt surface with newlineheat affected zone (HAZ) and thermal cracks in top surface layer comprising of recast (white) newlinelayer due to spark discharges. The white layer is the top most layers exposed to environment so it newlinehas dominant influence on its surface properties. This recast surface layer which is far harder newlinethan base material is generally removed by supplementary processes such as hand polishing, newlineetching or heat treatment, leading to increased cost and time. Critical analysis of the upper newlinesurfaces shows the sign of alloying elements from the electrodes and contaminations from the newlinedielectric. This observation led to the method of deliberate surface modifications and treatments newlineto improve surface qualities such as residual stresses, micro hardness, corrosion properties etc on newlinethe EDM surfaces. A relatively new advancement in this direction is to use some additives newlinepowders suspended in the dielectric fluid of EDM to fulfill the requirement of minimum surface damage, enhance machining rates and improving surface properties. This new hybrid machining newlineprocess is called abrasive mixed electrical discharge machining (AEDM).