Experimental Investigation on Surface Modification with Powder Mixed Electric Discharge Machining

Abstract

Study on the research problem entitled “Experimental Investigation on Surface Modification with Powder Mixed Electric Discharge Machining” was conducted in the M.E.D., T.I.E.T., Patiala during the year 2006. Electrical discharge machining (EDM) is a manufacturing process by which tool cuts the required shape into the workpiece within a dielectric fluid. In the past, research has been done to develop and improve different models of the material removal from both tool and workpiece. Recently, a new process of surface modification by EDM process has been evolved by mixing some suitable material in powder form into the dielectric fluid of EDM for improving the life of metal. This new process is called Powder Mixed EDM (PMEDM). In the present investigation, two powders i.e. Aluminium oxide (Al2O3) and Silicon carbide (SiC) both @ 2, 8 and 16 g/l, were mixed in dielectric fluid with a view to study the effect of powders suspended into the dielectric fluid on the surface modification. Machining parameters viz., dielectric type, peak current, pulse duration, concentrations of powders, etc. were changed to explore their effects on machining performance as judged from the material removal rate (MRR), tool wear rate (TWR), surface roughness (SR), hardness and micro-structure. The surface roughness and hardness of workpiece were improved by optimizing various combinations of Al2O3 and SiC powders mixed in kerosene with different ratio. The combination of powders weighing112 g mixed in 7 litres of kerosene was found to be the best. The quality of machined surface was analyzed by using the scanning electron microscope (SEM). SR values of machined surface of each workpiece were measured using the surface roughness measuring instruments “perthometer” and “surf test”. The use of powders was evaluated by recording observations on various input and output parameters. Addition of SiC powder @ 16 g/l into the dielectric was found to be the best as judged from its effects effect on various parameters. The same process also imparted the maximum hardness to the machined surface of the workpiece. It was further observed that MRR value was more in simple process as compared to Al2O3 and SiC processes. MRR was the maximum in straight polarity process as compared to reverse polarity process while TWR was higher in general but the highest in case of SiC when used at the concentration of 16 g/l.