Influence of Processing Parameters on Surface Properties of SKD61 Steel Processed by Powder Mixed Electrical Discharge Machining

Abstract

Many studies have carried out on the characteristics of surfaces processed by PMEDM with various powders. However, limited works have used the tungsten carbide powder in the PMEDM process and investigated its effects on the surface properties. In this research, the influence of main process parameters, including the peak current (Ip), the pulse on time (Ton), and the powder concentration (Cp) on surface properties—i.e., surface roughness (Ra), microhardness of surfaces (HV), and surface morphology of SKD61 steel machined by PMEDM with tungsten carbide powder, was explored in two modes: the fine-finish mode and the semi-finish mode. The results show that the peak current, the pulse on time, and the powder concentration have a noticeable influence on surface properties. The surface roughness, the microhardness of surfaces, and the surface morphology at the small peak current (Ip =1 A) and the short pulse on time (Ton =16 µs) were improved better than those at the large peak current (Ip=4 A) and the long pulse on time (Ton =200 µs) with all powder concentrations. The best improvement of the surface roughness at Ip=1 A; Ton=16 μs; Cp=40 g/l is 0.471 ± 0.011µm with a reduction of 57.984% as compared to the normal EDM. The set of processing parameters {Ip=1 A; Ton=16 μs; Cp=60 g/l} has the most positive effect on the improvement of microhardness and surface morphology: The microhardness was enhanced up to 825 ± 19 HV with an increase of 129.167% as compared to the normal EDM. The surface morphology had the smooth surface, the few micro-cracks, the few voids, the few droplets, and the few globules of debris as compared to that of other process parameters and the normal EDM.