Effect of powder metallurgy Cu-B₄C electrodes on workpiece surface characteristics and machining performance of electric discharge machining

Abstract

The main aim of this study is to produce new powder metallurgy (PM) Cu-B 4 C composite electrode (PM/(Cu-B 4 C)) capable of alloying the recast workpiece surface layer during electric discharge machining process with boron and other hard intermetallic phases, which eventually yield high hardness and abrasive wear resistance. The surface characteristics of the workpiece machined with a PM/(Cu-B 4 C) electrode consisted of 20 wt% B 4 C powders were compared with those of solid electrolytic copper (E/Cu) and powder metallurgy pure copper (PM/Cu) electrodes. The workpiece surface hardness, surface abrasive wear resistance, depth of the alloyed surface layer and composition of alloyed layers were used as key parameters in the comparison. The workpiece materials, which were machined with PM/(Cu-B 4 C) electrodes, exhibited significantly higher hardness and abrasive wear resistance than those of machined with the E/Cu and PM/Cu. The main reason was the presence of hard intermetallic phases, such as FeB, B 4 C (formed due to the boron in the electrode) and Fe 3 C in the surface layer. The improvement of the surface hardness achieved for steel workpiece when using PM/(Cu-B 4 C) electrodes was significantly higher than that reported in the literature. Moreover, the machining performance outputs (workpiece material removal rate, electrode wear rate and workpiece average surface roughness (R a )) of the electrodes were also considered in this study.

Effect of Machining on Workpiece Surface Characteristics in Electric Discharge Drilling (EDD)

“…For the tested settings, RLT values increased with increasing I d and t on ( Table 3). The experimental RLT results obtained in this study are in agreement with the findings in [14], Cogun et al [12] and Li et al [3] studies. Figure 10 reveals the increasing R a values with increasing I d and t on for the tested workpieces.…”

“…Furthermore, the recast layer, where residual stresses are observed, contains micro-fractures and micro-craters [10,11]. Another mechanism effective on characteristics of the recast layer is the carbon accumulation which increases the hardness of the workpiece surface [12,13].…”

“…In EDM, the recast layer properties vary depend on various parameters like discharge current (I d ), pulse on time (t on ), pulse off time (t off ), type and characteristics of the dielectric liquid, addition of powder into dielectric liquid, application mode of the dielectric to the machining medium, electrode material and its' manufacturing method, physical properties of the workpiece [13]. In Cogun et al study [12], B 4 C powder added copper and pure copper electrodes, produced by powder metallurgy, were used as the electrodes whereas SAE1040 steel were used as workpiece. They reported increasing workpiece recast layer thickness (RLT) with increasing I d and t on .…”

Surface Characterization and Tribological Performance Analysis of Electric Discharge Machined Duplex Stainless Steel

“…Both the machined substrates showed micro and macropores and re-solidified metallic droplets on the surface. It is observable from the images ( Figure 4 a,b) that higher spark energy (Spark Energy = Current × P-on × Voltage) generate pores along with small peaks and valleys on the EDT surface [ 39 , 40 ]. The presence of the pores and molten metal droplets on the surface promotes the biological performance of the substrates [ 41 ].…”

Micro-hardness evaluation for surface alloying of H11 die steel with Cu–Cr–Ni powder metallurgy tool in electrical discharge machining

“…Many methods are reported to improve a particular surface property by alloying the workpiece surface with suitable elements using EDM. Researchers have used sintered or semi-sintered powder metallurgy (PM) electrode, [5][6][7] powder suspended in a dielectric fluid [8][9][10][11] and suitable dielectric fluid 12 for surface alloying. Research is going on to investigate the performance of tool electrode manufactured by PM process.…”