This paper presents the investigation of minimum recast layer of zirconium oxide (ZrO2)
due to micro-EDM using EDM-3 synthetic oil as dielectric fluid and tungsten as the tool electrode
with control parameters of rotational speed and gap voltage. The investigation was performed using
multi-process micro machine tools DT 110. The recast layer thickness was observed using scanning
electron microscope and its hardness was measured using micro-Vickers hardness tester. The
hardness data were analyzed and an empirical model was developed. The optimum value for
minimum recast layer hardness was 873.46 Hv with rotational speed of 395 rpm and gap voltage of
110 V
