Study of surface integrity using the small area EDM process with a copper-tungsten electrode

The present study performs the small area electro-discharge machining (EDM) process with a low wear-rate copper-tungsten electrode of diameter 1.5 mm to establish the influence of the EDM parameters on various aspects of the surface integrity of AISI 1045 carbon steel. The residual stress induced by the EDM process is measured using the Hole-Drilling Strain-Gage Method. The experimental results reveal that the values of material removal rate (MRR), surface roughness (SR), hole enlargement (HE), average white layer thickness (WLT), and induced residual stress tend to increase at higher values of pulse current and pulse-on duration. However, for an extended pulse-on duration, it is noted that the MRR, SR, and surface crack density all decrease. Furthermore, the results indicate that obvious cracks are always evident in thicker white layers. A smaller pulse current (i.e. 1 A) tends to increase the surface crack density, while a prolonged pulse-on duration (i.e. 23 μs) widens the opening degree of the surface crack, thereby reducing the surface crack density. The EDM hole drilling process induces a compressive residual stress within the workpiece. A linear relationship is identified between the maximum residual stress and the average white layer thickness. It is determined that the residual stress can be controlled effectively by specifying an appropriate pulse-on duration.