Taguchi analysis of surface modification technique using W-Cu powder metallurgy sintered tools in EDM and characterization of the deposited layer

Abstract

The present study describes an experimental research on surface modification during electrical discharge machining (EDM) by depositing a hard layer over the work surface of C-40 grade plain carbon steel using specially prepared powder metallurgy compact tools. The investigated process parameters were composition, compaction pressure, sintering temperature, pulse on-time, peak–current setting, and duty factor. Measurements of deposited layer thickness, mass transfer rate, tool wear rate, surface roughness and microhardness were undertaken on the EDM-ed specimens. Different studies like X-ray diffraction, optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were carried out to ascertain the characteristics of the deposited layer on the work surface. These analyses confirmed the presence of the tool materials in the work surface layer. At first, an L-16 orthogonal array was applied as Taguchi DOE technique and the ANOVA was done to study the effects of pertinent process parameters. An optimum condition was achieved using overall evaluation criteria. Later on, a detailed study was carried out to get a smooth and regular deposition of material. The characterization of the deposited layer is presented. The deposited layer with a wide range of average layer thickness of 3–785 μm, enriched with tool materials (W and Cu) and with the formation of tungsten carbide, and having microhardness of 9.81–12.75 GPa at the hardest zone was successfully deposited over the work surface.