Die steel surface layer quality improvement in titanium μ-powder mixed die sinking electrical discharge machining

Abstract

In practice, the improvement of surface roughness (SR) after die sinking electric discharge machining (EDM) is simple and inexpensive when compared with the microhardness of machined-surface layers (HV). In addition, when HV is low, the improvement of SR will be less effective and have no significance to the mold surface layer. Therefore, the HV of molds after die sinking EDM is improved and plays a more important role than the improvement of SR. Currently, powder-mixed die sinking EDM is a technological solution that can improve both the HV and SR simultaneously. However, SR is given a priority criterion popular choice for many studies into powder-mixed die sinking EDM. In this current study, the researchers improve the quality of the steel surface layer of the mold using titanium (Ti) powder-mixed die sinking EDM. In the research, HV is selected as a criterion to optimize input parameters, and SKD61, SKD11, and SKT4 mold steels as well as Cu and Gr electrode materials are used. The effects of the workpiece material (A), electrode material (B), electrode polarity (C), pulse-on time (D), pulse-off time (F), current (E), Ti powder concentration (G), and some interactive A × B, A × G, and B × G to HV surface layers are analyzed and evaluated. Finally, the Taguchi method is used to optimize the parameters. Results indicated that parameters such as the electrode material, the pulse-on time, the concentration powders, A × G, and B × G significantly affect the HV. The Ti powder concentration has the largest effect on HV. When the powder concentration increased, HV was increased; its largest increase was 41.81%, and the optimal value of HVopt = 864.363 ± 61.68 HV at a Ti powder concentration of 10 g/l. The machined surface analysis of SEM and SR after powder-mixed die sinking EDM using Ti powder at optimal conditions showed that the quality of the surface layer was significantly improved. The qualities of surface layers, such us mechanical properties, topography, and the microstructure after EDM with titanium powder mixed into dielectric fluid, was significantly improved under optimal conditions for various mold steels.