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Machining hard-to-cut materials, such as cobalt (Co)-based superalloys, is a common problem in manufacturing industries. Background: wire electrical discharge machining (W-EDM) is one of the widely used cutting processes that causes layer (white layer—WL and heat-affected zone—HAZ) formation, and microcracks on the material's surface. Purpose: this study investigates the effects of WL and HAZ on the electrochemical grooving (EC grooving) performance of Co-based superalloys. Two different surface types (W-EDMed and VFed) were used in the experiments. Result: the experiments showed that material removal rate (MRR) values increased up to 212.49% and 122.23% for vibratory finished (VFed) and wire-electrical-discharge-machined (W-EDMed) surfaces, respectively. Conclusion: This result indicates the presence of HAZ and WL that prevent current transition between two electrodes. However, increased voltage causes an increase in surface roughness, with increment rates at 71.13% and 36.08% for VFed and W-EDMed surfaces, respectively. Moreover, for the VFed surfaces, the groove lost its flatness at the bottom after an approximately 100 µm depth due to the different electrochemical machineabilities of HAZ and real surface texture. This result can be attributed to the different microstructures (HAZ and surface texture) showing different electrochemical dissolution rates. Therefore, high-depth distance HAZ and WL must be removed from the workpiece. [ABSTRACT FROM AUTHOR]

The electrical discharge machining is a machining method applied when the workpiece material has a high hardness or the shape of the surface to be machined is to complicate to be obtained by a classical machining method. A problem of actual interest is the electrical discharge machining of small diameter external cylindrical surfaces in the case of materials characterized by high hardness. Among the distinct electrical discharge machining processes capable to be used in order to obtain small diameter cylindrical surfaces, a process based on the use of a plate type tool electrode was selected. A full factorial experiment with three independent variables and two experimental levels was designed and materialized to highlight the influence exerted by the pulse on time, pulse off time and peak current intensity on the heights of the cylindrical columns generated by electrical discharge machining. By mathematical processing of the experimental results, power type empirical mathematical models were established. The empirical models confirmed the strong influence exerted by the peak current intensity on the process output parameter. [ABSTRACT FROM AUTHOR]

Surface modifications of biomaterials play a vital role in matching the complexities of the biological system and improving the performance of bioimplants. Suitably customised surface modifications can substantially enhance the relation of material towards biocompatibility, bondability and host cells associations. In addition, materials surface engineering accelerates the progression and configuration of next-generation biomaterials and restorative gadgets. This review article dedicates to the surface modification techniques of several essential metallic biomaterials, viz. stainless steel, magnesium, titanium and chromium-cobalt. It presents the unique novel futuristic method of surface modification via electrical discharge machining (EDM) process which still awaits to prove its potential in the biomedical domain. Previously established research work on this nonconventional machining process elucidates that an adequate surface integrity can be achieved by control of crucial EDM process parameters such as pulse on, pulse off, current, polarity, dielectric medium and tool electrodes. Therefore, there is ample scope for the EDM process in examining the issues related to the synthesis and precise shaping of the bioimplants. [ABSTRACT FROM AUTHOR]

In this study, electrical discharge hole drilling processes was applied to DIN 1.2379 tool steel by using single-channel brass electrode and dielectric liquid which possess various level of temperature. In the study, the machining parameters were kept constant and the effect of the dielectric liquid temperature on the performance parameters such as material removal rate, electrode wear rate, white layer thickness, surface roughness, overcut in diameter and taper at the tip was examined. The results show that the decrease of dielectric liquid temperature improves performance parameters. The material removal rate was increased nearly 30%, surface roughness value R is improved from 4.8 to 2.7 μm, white layer thickness was decreased and the hole geometry is improved in terms of hole diameter and taper. [ABSTRACT FROM AUTHOR]

Efficient machining using wire electrical discharge machining (WEDM) technology is a compromise between cutting speed and resulting surface quality. Typical morphology of the surface machined by WEDM shows a plenty of craters caused by electrospark discharges produced during the cutting process. This work is focused on assessing the impact of machine setting parameters on quantitative and qualitative evaluation of the workpiece surface of aluminium alloy AlZn6Mg2Cu. Using metallography, the surface effects arisen during the process of wire spark erosion on cross-sections of preparations were studied. Using local spot EDX microanalysis, the chemical composition of the surfaces of the samples was studied. The attention was also paid to the highest height of profile of the craters, which were studied using 3D filtered images. [ABSTRACT FROM AUTHOR]

This paper describes the observation of EDM gap phenomena through a transparent electrode from the direction normal to the machining surface using a high-speed video camera. To visualize the gap, SiC single crystal was used as the electrode material since it is optically transparent and electrically conductive. It was found that more than 70% of the working surface was occupied by bubbles generated by discharge after a few hundred pulse discharges from the start of machining. Electrical discharge occurs not only in liquid but also in bubble and at the boundary between liquid and bubble. The probability of discharge occurrence per unit area of each atmosphere was highest at the boundary between liquid and bubble. Furthermore, the probability of discharge occurrence through debris particles located at this boundary generated by the last discharge was highest. [ABSTRACT FROM AUTHOR]

Machining fluid is a primary factor that affects the material removal rate, surface quality, and electrode wear of electrical discharge machining (EDM). Kerosene is the most commonly used working fluid in die sinking EDM, but it shows low ignition temperature and high volatility; if the improper operations are undertaken, it can cause conflagration. Using distilled water or pure water as the machining fluid in EDM, no fire hazard occurs, and the working environment is well; however, using distilled water or pure water as the machining fluid in EDM, the material removal rate of machining large surface is low, and the machine tool is easily eroded. Emulsion-1 and emulsion-2 used as working fluid in die sinking EDM are developed. The compositions of emulsion-1 and emulsion-2 are introduced. In comparison with kerosene, emulsion-1 and emulsion-2 used in EDM show high material removal rate, low surface roughness, high discharge gap, and good working environment. The electrode wear ratio in emulsion-1 is lower than that in kerosene. The electrode wear ratio in emulsion-2 is higher than that in kerosene. The effects of composition and concentration of emulsifier on the emulsion property and EDM performance have been investigated. The comparative tests of EDM performance with kerosene, emulsion-1, and emulsion-2 have been done. [ABSTRACT FROM AUTHOR]

This study performs experimental investigation into the application of abrasive jet polishing (AJP) to the surface finishing of electrical-discharge-machined SKD61 mold steel workpieces. The results indicate that the AJP processing conditions which optimize the surface quality of the SKD61 workpiece when polishing using #2000SiC abrasives are as follows: an abrasive material to additive ratio of 1:2, an impact angle of 30°, a gas pressure of 4 kg/cm2 (0.4 MPa), a nozzle-to-workpiece height of 10 mm, a platform rotational velocity of 200 rpm, and a platform travel speed of 150 mm/s. Under these processing conditions, a polishing time of 20 min is sufficient to reduce the surface roughness from an initial value of Ra = 1.7 μm to a final value of Ra = 0.27 μm, corresponding to an improvement of 84.12%. The experimental results demonstrate that the maximum attainable improvement in the surface quality of the polished workpiece is limited by a surface-hardening effect caused by the ball-impact phenomenon and the embedment of #2000SiC fragments in the workpiece surface. [ABSTRACT FROM AUTHOR]

This paper describes a new method of surface modification by electrical discharge machining (EDM). By using an ordinary EDM machine tool and kerosene fluid, a hard ceramic layer can be created on the workpiece surface with a Ti or other compressed powder electrode in a certain condition. This revolutionary new method is called electrical discharge coating (EDC). The process of EDC begins with electrode wear during EDM, then a kind of hard carbide is created through the chemical reaction between the worn electrode material and the carbon particles decomposed from kerosene fluid under high temperature. The carbide is piled up on a workpiece quickly and becomes a hard layer of ceramic of about 20 μm thickness in several minutes. This paper studies the principle and process of EDC systemically by using a Ti powder green compact electrode. Experiments and analyses show that a compact TiC ceramic layer can be created on the surface of the metal workpiece. The hardness of the ceramic layer is more than three times higher than that of the base body, and the hardness changes gradually from the surface to the base body. This method can find wide application in the fields of surface modification, such as the surface repairing and strengthening of cutting tools and molds. [Copyright &y& Elsevier]