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High electrical conductivity and low thermal conductivity are beneficial for the electrical discharge machining performance of ceramics. In this work, B 4 C–TiB 2 composites were prepared by spark plasma sintering of B 4 C–TiC–B powder mixture. The chemical reaction between TiC and B, together with subsequent selective matrix grain growth, expelled small in-situ generated TiB 2 grains to form conductive interlayers around large B 4 C grains. The unique microstructure significantly enhances the electrical conductivity of B 4 C–TiB 2 composites, especially at low TiB 2 content, while the ultrafine in-situ formed TiB 2 grains endow the composites with low thermal conductivity. The effects of TiB 2 content on the microstructure, mechanical properties, thermal & electrical conductivity of the composites were investigated. B 4 C–20 vol% TiB 2 composite exhibits excellent comprehensive performance, including a relative density, Vickers hardness, flexural strength, fracture toughness, room electrical and thermal conductivity of 98.6%, 28.15 GPa, 656 MPa, 5.46 MPa⋅m1/2, 1.08 × 105 S/m and 19.37 W/m⋅K, respectively. [ABSTRACT FROM AUTHOR]

Dense silicon carbide (SiC) composites with 0–30 vol% (ZrN-TiB 2) were fabricated by using liquid phase spark plasma sintering at a relatively lower sintering temperature (1800 °C) and shorter holding time (5 min). The effects of co-addition of ZrN and TiB 2 on densification, mechanical properties, and electrical conductivity of SiC ceramics were investigated. The reinforcement significantly enhanced density of sintered composites, while the phase analysis and microstructure confirm the suppression of β→α phase transformation in the SiC matrix. The fracture toughness ranged from 4.1 to 4.6 MPa·m0.5, hardness from 19.5 to 20.3 GPa, and electrical conductivity from 4.85 ×101 to 1.25 ×103 (Ω·cm)−1. Incorporating conductive reinforcements and nitrogen additives enhanced electrical conductivity. Successful wire-EDM cutting of SiC-ZrN-TiB 2 composites demonstrate the feasible alternative to conventional machining of non-oxide ceramics with a maximum material removal rate of 8.54 mm2/min. [Display omitted] [ABSTRACT FROM AUTHOR]

Surface formation in electrical discharge machining (EDM) involves melting, evaporation, re-solidification and crater overlapping. However, almost all existing models concerning surface formation in EDM only consider the thermal process and ignore hydrodynamic phenomena during machining. Herein, a novel three-dimensional thermo-hydraulic coupling model incorporating the arbitrary Lagrangian–Eulerian scheme was developed to address the above problem. The model comprehensively considered the surface deformation caused by melt flow, temperature-dependent material properties, phase changes and the effects of practical forces on melt pools to simulate surface formation on an anodic workpiece at a discharge current of 2 A. Simulation results demonstrate that during single-pulse discharge, molten material flowed radially to the crater periphery. The radial melt flow was driven by evaporation recoil pressure and thermocapillary force. The effect of evaporation recoil pressure on melt flow was gradually counteracted by that of surface tension after discharge ignition, and thermocapillary force became the dominant factor that maintained the existence of bulges around craters. During multiple discharges, the bulges generated by different discharges underwent superposition owing to the flow of molten material and subsequently formed surface peaks. The simulation results also provide the measurements of crater diameter, surface roughness and recast layer thickness, which are consistent with experimental results. The proposed modelling method can provide a useful reference for further investigations on surface integrity in EDM with minimal computing resource requirements. • A novel 3D thermo-hydraulic coupling surface formation model for EDM was proposed. • The effects of evaporation recoil pressure and thermocapillary force on melt pool dynamics in EDM were investigated. • Simulation results of multiple discharges show good consistency with experiment results concerning surface properties. [ABSTRACT FROM AUTHOR]

Arc plasma is the heat source in electrical discharge machining (EDM), it affects the material removal and discharge crater formation directly, so it is necessary to clarify its characteristics. However, it is challenging to understand the physical mechanisms behind each pulse discharge through experimental methods, as it is a transient, multi-physical process that occurs in a very short time and small gap. In this paper, a two-temperature model was proposed to investigate the characteristics of the arc plasma and the energy distribution considering the multi-physics fields in the steady state. In this model, the electrons and the heavy species of the arc plasma were considered separately in the energy conservation equations, so that the temperature of the electrons and heavy species can be calculated separately. Besides, the velocity distribution, pressure distribution, electrical potential distribution, and diameter of the arc plasma, as well as the heat flux distribution and the energy distribution into the anode and cathode were analyzed. Then the variations in arc plasma properties and energy distribution with different discharge conditions were studied. The results showed that, at a lower discharge current, the electron temperature was higher than the heavy species temperature, which means that the arc plasma did not reach a local thermodynamic equilibrium (LTE) state under these discharge conditions. To validate the simulation results, the arc plasma was observed with a high-speed camera, and the diameter of craters on the surface of both the cathode and anode was measured with single-pulse discharge experiments. The experiment results were consistent with the simulation results. • A two-temperature model was established to study the arc plasma in EDM. • The temperature of electrons and heavy species of arc plasma was obtained. • The arc plasma did not reach the local thermodynamic equilibrium state under the given simulation conditions. • The energy distribution ratio into the anode, cathode, and dielectric were calculated, respectively. • The arc plasma characteristics and the energy distribution under different discharge conditions were studied. [ABSTRACT FROM AUTHOR]

In recently, titanium and its alloys have been used in a large number of medical implants due to their excellent biological qualities. However, infections brought on by their biological inertness have emerged as a challenging issue for clinicians across a range of specialties. On the other hand, improper use of antibiotics has increased bacterial resistance, which has made the issue of infections brought on by titanium implants worse. The preparation of implants with antimicrobial capabilities has emerged as a key research area in the effort to address this issue at its source. However, present techniques for preparing antimicrobial surfaces are pricy, ineffective, and harmful to the environment, thus cannot be used extensively in industrial manufacturing. In this study, the bionic shark skin's antibacterial rhombic surface was prepared in a single step using the WEDM processing. The samples were then described, and the outcomes were examined using XRD, FE-SEM, and EDS. By using the plate coating method and SBF immersion assays, the samples' bioactivity and antibacterial capacity were assessed. Due to the high temperature produced during the WEDM process, which enables the tool electrode to melt and metallurgically link with the titanium alloy substrate surface, the primary crystalline phase of the antibacterial surface is CuTi 2. After 1 h of incubation on the sample surface, the samples' antibacterial rate was 93%. The antibacterial property of the sample also attained an ideal 98.4% when acid etching was carried out using a 20%wt HNO 3 solution. The Ti on the sample surface had no discernible impact on the effectiveness of the antibacterial. Additionally, the simulated liquid immersion findings demonstrated that the sample pieces made using this approach exhibited good bioactivity. [ABSTRACT FROM AUTHOR]

Amorphous alloys are a new type of multi-functional advanced material with the properties of general metal materials and glass, which are also called metallic glasses. They have good comprehensive properties, such as a wide application range, low cost, and high reusability. Using reasonable process parameters, non-traditional machining can not only realize the machining of complex amorphous parts, but also avoid the crystallization and oxidation of amorphous alloys, realizing tasks that cannot be accomplished by traditional machining. Therefore, this review systematically summarizes the research status and development potential of amorphous alloys fabricated using non-traditional machining methods. First, we introduce the principles of laser machining, ultrasonic machining, electrical discharge machining, electrochemical machining, and other non-traditional machining methods for amorphous alloys. Subsequently, the influence of the machining parameters and other external conditions on the machining effect is summarized. The machining cost, machining efficiency, and environmental impact of these non-traditional machining methods were compared. Finally, non-traditional machining technology for amorphous alloys is summarized and discussed. • The processing principles of non-traditional machining methods are summarized. • The influences of processing parameters on the machining effect are reviewed. • Costs, effects, and pollution of non-traditional machining are compared. • The limitations or shortages of non-traditional machining methods are summarized. [ABSTRACT FROM AUTHOR]

This study investigated the machinability of AISI H13 hot work tool steel with a hardness of 54 HRC, which has been deep cryogenically treated using the electro-erosion machining technique, one of the unconventional manufacturing methods. The machinability parameters used in the study were determined as current (4, 8 and 12 A), pulse time (200, 300 and 400 µs) and three different electrodes (Copper, Graphite and Tuncop). The experimental design was designed according to the Taguchi L 27 model, and machinability tests were carried out to examine the results obtained from the experimental study both experimentally and statistically. When the literature was examined, it was seen that cryogenic treatment was generally applied to electrode materials, and only surface roughness and material wear amounts were examined as output parameters. The original value of the study is the interpretation of the results by applying cryogenic treatment to the test material and exploring the surface roughness and material wear amount, as well as the hole diameters and criterion diameters formed on the treated surfaces after the EDM process. As a result of the study, it was observed that the surface roughness value, the hole diameter, the amount of material wear, and the crater diameter increased with the increase in ampere and impact time. The lowest surface roughness value was 2.266 µm in the graphite electrode material at 4 amps and 200 µs impact time and the highest wear amount was realized as 0.555 g in the copper electrode material 12 amps and 400 µs impact time. The smallest hole diameter was 12.254 mm with a tuncop electrode with a pulse duration of 4 amps and 200 µs, and the lowest crater diameter was 127.301 µm with a graphite electrode at a current of 4 amps and a pulse duration of 200 µs. When the signal-to-noise ratios were examined, the optimum machining parameters for surface roughness, hole diameter, material wear amount, and crater diameter were determined as A 2 B 1 C 1 , A 1 B 3 C 3 , A 3 B 1 C 1 , and A 3 B 1 C 1 , respectively. When the ANOVA results are examined, it is determined that the most effective parameter for the surface roughness is of the current value with 86.54%, the most effective parameter for the hole diameter is the electrode material with 85.20%, the most effective parameter for material wear amount is the electrode material with 45.67% and the most effective parameter for the crater diameter is current value with 75.35%. [ABSTRACT FROM AUTHOR]

Sinking electrical discharge machining (EDM) is a vital machining technology used in modern mechanical manufacturing. However, the conventional sinking EDM, which utilizes an oil-based working medium, presents disadvantages such as low machining efficiency, harmful gas emissions, and fire hazards. Although researchers have attempted to use pure water as the working medium, pure water cannot replace oil and has not yet been industrially applied as a working medium because of its low machining efficiency and thick surface recast layer. Herein, we propose sustainable and green sinking EDM utilizing foam water (SEDM-FW) as the working medium, a method that uses pressurized foam water, ultrastrong energy discharge, and upward electrode feeding. The proposed method is cost effective, and its machining efficiency is more than three times higher than that of the conventional sinking EDM at the same peak current. The use of foam water instead of oil as the working medium solves environmental pollution problems associated with the conventional sinking EDM. In terms of environmental performance, the SEDM-FW produces gas byproducts that do not contain any harmful components, including 1,3-butadiene and benzene, which are present in the conventional sinking EDM. Compared with using pure water, using foam water as the working medium in conjunction with an appropriate gas-to-liquid ratio can double the machining efficiency, reduce the thickness of the recast layer by more than half, and reduce the size of surface microcracks. Using gas-dominated foam water, surface microcracks can be eliminated, and a zero-thickness recast layer can be achieved. [Display omitted] • A sustainable and green sinking EDM method (SEDM-FW) is proposed. • Foam water is used as the working medium, which replaces conventional oil and pure water. • Gas byproducts of SEDM-FW are completely harmless to humans and environment. • A proper gas-to-liquid ratio has higher MRR, lower REWR, and good surface integrity. • Gas-dominated foam water can eliminate microcracks and achieve zero-thickness recast layers. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond is widely used in many fields including ultra-precise machining, optical material and semiconductor electronic devices due to its excellent physical properties. However, traditional mechanical processing methods of polycrystalline diamond leads to severe tool wear, low efficiency and high costs. Although electrical discharge machining can overcome some limitations, it usually exhibits a low material removal rate and poor surface quality. This study aims to explore the effect of graphene powder and ultrasonic vibration on polycrystalline diamond by electrical discharge machining. It was found that the synergistic effect of graphene powder and ultrasonic vibration can achieve a good surface quality. The results show that ultrasonic-assisted powder mixed electrical discharge machining can obtain the smallest surface roughness (1.98 μm) at low parameter and the biggest material removal rate (0.773 mg/min) at high parameter compared with ultrasonic assisted electrical discharge machining and powder mixed electrical discharge machining. In addition, after ultrasonic-assisted powder mixed electrical discharge machining, the minimum value (0.807) of I D /I G is obtained. For polycrystalline diamond, this study also proposes a removal mechanism that diamond converts into graphite and is peeled under tensile stress. [Display omitted] • The U-PMEDM for PCD benefits from the synergistic of ultrasound and graphene. • Ultrasonic vibration acts on the chemical bonds in the graphene layers. • Graphitization of diamond occurs and graphene is peeled off under tensile stress. [ABSTRACT FROM AUTHOR]

Boron carbide (B 4 C) composites containing 0–10 wt.% graphene nanoplatelets (GNPs) were consolidated using hot pressing at 1950 °C for 60 min under 30 MPa in an argon atmosphere. Their electrical discharge machining (EDM) characteristics were evaluated for the first time. Additionally, the effects of GNPs on the microstructure, electrical conductivity, material removal rate (MRR), and surface roughness (R a) of B 4 C composites were investigated. The results show that the B 4 C composite containing 10 wt.% GNPs exhibited the highest electrical conductivity of 4997 S·m−1 because of the formation of GNPs conductive networks. Under a fine machining condition, the MRR of the B 4 C composite was enhanced by 43.5 % (from 6.55 to 9.40 mm3 min−1) compared with that of monolithic B 4 C. Furthermore, the R a decreased to 1.12 μm, which was significantly lower than that of pure B 4 C (2.44 μm). Scanning electron microscope and energy disperse spectroscopy analysis of the EDM surfaces were used to determine that the main material removal mechanisms for B 4 C composites with less than 2 wt.% GNPs were spalling and melting. As the GNPs content increased, B 4 C grain fallout, melting, and evaporation became more dominant. The other mechanisms, including thermal shock and oxidation, are also discussed in detail. [ABSTRACT FROM AUTHOR]

The significantly increased stability of third-generation semiconductors, both mechanically and chemically, presents a significant challenge to traditional wafer grinding. This study develops pure electrical discharge machining as an alternative for non-contact wafer grinding and thinning to achieve high precision and low cost. This method employs a copper-made rotary cup wheel as the tool electrode to replace the conventional diamond wheel to realize electrical discharge grinding. A prototype is built to evaluate the new process with single-crystal SiC. Aiming at ultra-precision machining, the material response of SiC to both single and consecutive discharge is elucidated. The influencing mechanism of pulse conditions on hard, brittle crystalline SiC material is demonstrated via experiments and simulation. Further, the material removal behavior, grinding stability, surface integrity, wafer shape accuracy, and process-induced subsurface damage are comprehensively investigated via single and consecutive discharge experiments under various conditions. In addition, the extreme precision that is achievable by contemporary EDM technology is explored. As a result, a 30 μm thin Φ 20 mm SiC wafer with a subsurface damaged layer <1 μm was obtained, showing the potential of EDM for the processing of third-generation semiconductor wafers. • A non-contact wafer grinding/thinning method by pure EDM is first presented. • The material response of SiC to both single and consecutive discharge is elucidated. • Ultra-short-pulse enhances the wafer grinding efficiency and surface integrity. • The grinding precision and thinning limit by contemporary EDM technology are explored. • EDM shows high potentials for processing next-generation ultra-hard semiconductor wafers. [ABSTRACT FROM AUTHOR]

• The feasibility of machining of CAHL composite using RTEDµD was established. • The machining time increased with the increase of aramid layers in the CAHL. • Better dimensional accuracy obtained at the exit of the micro-holes. • Material removal was assisted by pyrolytic carbon and copper deposition. This study reports the pioneering investigation on rotary tool-assisted electrical discharge micro-drilling (RTEDµD) of carbon-aramid hybrid laminate (CAHL). The machining times (MT) for fabricating one through-micro-hole (depth: 1500 µm) on the CAHL containing 1, 2, and 3 layers of aramid were 785 s, 800 s, and 840 s respectively. The MT increased by 20 % for the CAHL containing 3 aramid layers compared to carbon fiber reinforced polymer (CFRP). The diameter of the holes was within 730–900 µm and an overcut of 4.28 %–28.57 % was observed. [ABSTRACT FROM AUTHOR]

The surface modification of Ti–6Al–4V alloy was achieved by using an electrical discharge machining (EDM) surface modification technology under the action of pulsed discharge to induce an in-situ synthesis reaction between the molten metallic material and the ionized elements in the atomized medium. In this study, nitrogen and urea solutions are used as the gas-liquid phases of the atomization medium. ANSYS simulation software was used to simulate and analyze the interpolar pressure and flow field of the different electrodes. The effect of different electrode forms on the EDM surface modification layer was investigated by designing comparative trials. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and other detection methods were used to characterize the process indicators, such as surface morphology, roughness, hardness, and wear resistance of the reinforced layer. It was found that a thick and uniform continuous layer can be obtained on the Ti–6Al–4V alloy substrate using multi-channel electrode machining, and the thickness is about 65 μm. XRD analysis indicates that the reinforced layer mainly contains TiN, Ti 2 N, Ti 2 AlN, Ti 2 O, and CuO phases. The samples with reinforced layers were shown to have higher hardness (1578 HV) and better wear resistance than the titanium substrates. The main wear mechanism is spalling wear and light oxidation wear. • Near-dry EDM surface modification using different channel electrodes. • Evaluating the effect of electrode forms on the state of the interpolar flow field distribution. • The multi-hole electrode contributes to the formation of modified layers. • The modified layer of multi-hole electrode has better surface morphology and performance. [ABSTRACT FROM AUTHOR]

A micro rod machining method which can switch between electrical discharge machining (EDM) and electrochemical machining (ECM) by attaching/detaching a diode to/from a bipolar pulse generator in parallel to the working gap was newly developed using a wire electrode made of tungsten. The problem of the wire electrode wear was eliminated by the use of the wire electrochemical turning (WECT) method in which the tungsten wire electrode is continuously running. The ultra-short bipolar pulse current was generated by the electrostatic induction feeding method where a pulse voltage is coupled to the working gap through a feeding capacitance. The machining characteristics of three types of wire guide; disk-shaped WC guide, laminated wire guide and cylindrical acrylic guide, were studied. The experimental results showed that the cylindrical acrylic guide has the best machining characteristics without the influence of guide wear and with less stray current flowing through the working gap. Using the cylindrical acrylic guide, the influences of the feeding capacitance C 1 , and the total amplitude of the pulse voltage on the machining characteristics were studied. Finally, a stainless steel SUS 304 micro-rod with a high aspect ratio of 14 was fabricated efficiently by using the EDM and ECM modes for rough and finish machining in sequence with the same setup, pulse generator, and neutral electrolyte. • EDM and ECM modes can be switched in neutral electrolyte by attaching/detaching a diode in parallel to the working gap. • The problem of the tool electrode wear was eliminated by the use of the WECT method. • The machining characteristics of different types of wire guide are studied. • Micro-rod of high aspect ratio is machined using the EDM and ECM in same neutral electrolyte. [ABSTRACT FROM AUTHOR]

[Display omitted] • Deterministic cellular lattice structures of IN718 are fabricated through LPBF. • Through-holes EDM drilling is performed on LPBF-fabricated lattice structures. • Machined holes show dimensional variability due to pores, nodes, and lattice defects. • Near-circular through-holes machined by optimizing EDM parameters and electrode positioning. Additive manufactured (AM) metallic lattice structures are being largely explored for different engineering applications. The fastening, implantation, and installation of such lattice structures demand secondary processing. In the current work, through-hole drilling is performed using electrical discharge machining (EDM) on Inconel 718 (IN718) lattice structures fabricated by laser powder bed fusion (LPBF). The challenges in EDM hole drilling have been encountered and uncertainty in the machined holes owing to periodically open pores and nodes in the lattice structures sizes has been identified. Finally, an experimental strategy has been proposed for near-circular hole drilling by design optimization and tool positioning with respect to the cellular structures. [ABSTRACT FROM AUTHOR]

• Shock location correlation to direct contact condensation stability. • CFD analysis of nozzle features. • Stability study on chamfers and defects in DCC nozzles. • Stability regime maps for multiple types of nozzles including orifice, converging, and converging diverging nozzles. Direct contact condensation (DCC) is an efficient way of transferring heat between fluids' vapor and liquid phases by mixing them directly rather than using a device like a heat exchanger. However, in the field, DCC may produce destructive and unwanted vibrations due to the instability of the gaseous plume condensing in the process fluid under certain conditions. Previous research on this topic has focused on correlating the flow conditions of the liquid and vapor phases to engineering quantities, such as the heat transfer coefficient, plume length, stability, and the dominant frequency exhibited by the DCC process. The present study investigates the impact of nozzle geometry on plume stability. It was motivated by the drastic difference observed experimentally between the stability of two identically designed nozzles with slightly different microfeatures. Tests were performed with several nozzle geometries, including converging/diverging, straight, and converging nozzles. The results from these experiments show that a nozzle with a supersonic flow at the exit plane is more likely to be stable than one with a subsonic exit flow. It is, therefore, possible to correlate the pressure ratio across the nozzle and nozzle geometry to the stability of the plume. This understanding allows a DCC nozzle geometry to be analyzed and designed for high stability with relatively simple one- and two-dimensional compressible flow modeling tools capable of resolving only the single-phase, compressible flow in the nozzle itself [ABSTRACT FROM AUTHOR]

Titanium alloys, such as Ti6Al4V, are widely employed in the biomedical industry for implant applications due to their favourable properties. However, these alloys can experience long-term corrosion in the presence of bodily fluids, which is a critical concern for implants as it affects their timespan. Therefore, this study aimed to examine the corrosion resistance of Ti6Al4V in body fluid. Highly desirable electrical discharge machining (EDM) techniques used for Ti6Al4V sample preparation with three different conditions (oil, deionized water, and hydroxyapatite mixed in deionized water). Corrosion was assessed using electrochemical analyses, with microstructural analysis. Results indicated that the samples produced using water and oil had the best and lowest corrosion resistance, respectively. Protective oxide layer formed during the EDM in water while heterogeneous surface was produced for EDM in oil. The increase in capacitance leads to the thickening of the oxide layer, thereby enhancing the corrosion resistance. • Capacitance and bath influence on the corrosion resistance of the EDMedTi6Al4V in SBF. • The passive film was produced in aggressive environment (water and HA), increasing the Ti6Al4V corrosion resistance in SBF. • The capacitance increment generated thicker oxidised layer on Ti6Al4V, improving the corrosion resistance in SBF. • Corrosion mechanism of the EDMed and non-EDMed samples in SBF was influenced by EDM before and after transpassivation. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) of electrically conductive ceramics offers the possibility to manufacture customized ceramic components from sintered blanks. In this study two different yttria neodymia co-stabilized TZP materials containing 28 vol% niobium carbide were manufactured by hot pressing at 1275 °C–1400 °C and axial pressure of 60 MPa and compared to a 3Y-TZP based reference. The co-stabilized ceramics offer a strength up to 1250 MPa and a hardness of 14 GPa. The fracture resistance can be tailored between 7.4–9.7 MPa√m by variation of the yttria/neodymia ratio and the sintering temperature. These composites, however, require an exact setup of machining parameters. Die sinking EDM experiments revealed that the dominant material removal mechanism is melting. Machined surfaces can achieve low roughness Ra =0.3 μm combined with material removal rates of 1.5 mm³/min. The choice of excessively high energy parameters in EDM may lead to crack formation, spallation and phase accumulation during re-solidification. [ABSTRACT FROM AUTHOR]

Crystallization fouling adhered on the heat transfer surface is a serious problem. Here, we report an anti-fouling heat transfer surface prepared by magnetron sputtering (MS) a-C film on an electrical discharge machining (EDM) Cu surface (MES). Microstructure, chemical composition, wettability and anti-fouling property of the resulting modified surface were analyzed by SEM, EDS, XRD, XPS, Raman, Contact angle measurement, Atomic Absorption Spectroscopy and homemade heat transfer performance testing device. The formation of CaCO 3 fouling and the anti-fouling mechanism of the as-prepared surface are also discussed. The results show that the surface prepared by EDM and MS displays a micro/nano structure with a-C film deposited on it. The combination of micro/nano structure and the low surface energy a-C film endows the MES with higher contact angles for both water and glycerol as well as superior anti-fouling property than the polished Cu surface (PS) and the EDM Cu surface (ES). This work offer an effective strategy and promising application for fabricating anti-fouling heat transfer surface. • Anti-fouling surface is modified by magnetron sputtering and EDM. • The modified surface is characterized with a-C film coated on micro/nano structure. • The modified surface shows remarkable hydrophobicity and oleophobicity. • The modified surface performs lower fouling resistance and longer induction period. [ABSTRACT FROM AUTHOR]

• The corrosion behavior of the Ni-based single crystal superalloy and its recast layer is investigated by electrochemical techniques in NaNO 3 solution. • The recast layer surface forms a stronger passivation film with high corrosion resistance. • Only γ phase exists in the recast layer, the surface bugle consists of oxide, and there is shedding during the electrochemical dissolution. • The γ phase on the surface of Ni-based single crystal superalloy is preferentially dissolved, leaving the block γ' phase. Ni-based single crystal superalloy is favored for turbine blades. In order to adapt to the high temperature of the working environment, film cooling technology is widely used. The film cooling holes of turbine blades require no recast layer residuals and high machining efficiency. Combined or hybrid methods of electrical discharge machining (EDM) and electrochemical machining (ECM) show prospective applications. Here, the recast layer generated by discharge during high-speed drilling is removed by electrochemical dissolution. But the dissolution behavior of it is not investigated. In this paper, The anodic electrochemical behavior of a Ni-based single crystal superalloy and its recast layer in NaNO 3 electrolyte is reported, and the surface morphology change of electrochemical dissolution is elucidated. The results showed that the γ' phase disappeared in the recast layer after EDM. Its oxide content within the passivation film is significantly elevated, exhibiting a stronger corrosion resistance than the matrix. For the material removal characteristics, the crater on the recast layer surface preferentially undergoes corrosion, adopting an alveolate structure, with the bulges later dissolved or removed by shedding due to oxide enrichment. For the matrix, the γ phase undergoes electrochemical dissolution, leaving a block γ' phase. A qualitative electrochemical dissolution model is established. [ABSTRACT FROM AUTHOR]

Electrochemical jet machining (EJM) has attracted considerable attention in alloy manufacturing due to its versatility and flexibility. However, for EJM of titanium alloys, the Material Removal Rate (MRR) is low due to the formation of the refractory oxide layer and the non-participation of end face of tool electrode. In order to improve the MRR in this study, a novel hybrid method called gas electrical discharge and electrolyte jet simultaneous machining, which combines electrical discharge machining (EDM) and electrochemical jet machining (EJM), is proposed to effectively reduce the oxide layer and promote the participation of the end of electrode tool in machining process. In the hybrid EDM-EJM method, an instantaneous high voltage spark discharge breaks down the air between two electrodes to remove instantaneously the oxide layer, and then the workpiece is machined to a smooth surface by subsequent and highly efficient EJM. Each point on the workpiece surface is treated successively via EDM and EJM, so the entire surface is machined by the two separate machining modes. The EDM and EJM act simultaneously on the workpiece and in synchronization throughout the machining process. Also, the end face of the workpiece contributes to material removal, hence the MRR is improved. Due to the periodic change of the machining voltage at the EDM stage, the reflection angle of the flowing electrolyte also changes periodically, and this is conducive to increasing fluctuations in the flow of electrolyte and hence accelerating the removal of the electrolysis products. Our studies shows that this new combined approach improves not only the MRR, but also greatly reduces erroneous corrosion effects and reduced the surface roughness Ra from 0.800 µm to 0.177 µm. [Display omitted] • A novel hybrid method is proposed to effectively promote the participation of the end of the tool in machining. • EDM and EJM act simultaneously on the workpiece and in synchronization throughout the processing. • The flow of the deflected electrolyte was periodic in line with the periodic change in voltage. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Superhydrophobic surface is fabricated on electrical discharge machining (EDM) surface by electrochemical etching. • EDM superhydrophobic surface is shown a hierarchical micro-nanostructure, where EDM surface is basement. • EDM is used as a pretreatment process for the fabrication of superhydrophobic surface, enhances the performance. • The superhydrophobic surface on EDM functional unit of parts shows better application. Abstract Fabrication of superhydrophobic surface (SHS) on metal can effectively enhance its utility value. Herein, electrochemical etching for the electrical discharge machining (EDM) surface of beryllium copper (Be-Cu) alloy is carried out in the hydrochloric acid electrolyte, to obtain a hierarchical micro-nanostructure. After modification by stearic acid, the contact angle is up to 167.1 ± 2.6° and the sliding angle to 2.4 ± 0.7°. The microstructure constructed by EDM improves the quality of the SHS availably. The corrosion and abrasion resistance tests show that the performance is significantly higher than that without EDM. EDM can be used as a pretreatment process for the fabrication of SHS. It can also be applied to the EDM functional unit of parts to achieve specific functions. In addition, EDM for hole, the inner wall of the superhydrophobic hole was obtained, confirmed the excellent self-cleaning performance. This method has a good application prospect in the fabrication of SHS of metallic engineering materials. [ABSTRACT FROM AUTHOR]

Abstract Electrical discharge machining is a significant non-traditional technique, widely used in the precise manufacturing field. However, the electrical discharge machining process possesses plenty of energy consumption and hazardous exhaust emissions. Since a sustainable machining technique, external magnetic field assisted, could dramatically develop sustainable machining performance of electrical discharge machining process, this paper presents a comparative study energy efficiency and environmental impact in magnetic field assisted electrical discharge machining and conventional electrical discharge machining. A novel thermo-physical model was proposed to calculate energy distribution under the single/continuous discharge, which was verified by a series of corresponding experiments. Then, based on simulation and experimental methods, a comparative study on the magnetic field assisted electrical discharge machining and conventional electrical discharge machining was conducted to analyze the discharge energy flowing and temperature distribution of workpiece, electrode tool and debris. Moreover, the effects of external magnetic field on the machining performance, environmental impacts and energy efficiency were presented. Eventually, it can be found out that the effect of magnetic field contributes to increasing energy utilization efficiency by 15.2%, material erosion efficiency by 22.6%, and material removal rate by 21.9%. To balance energy efficiency and surface roughness (Ra), the optimal parameter combination is obtained as below: magnetic field intensity: 0.2T, discharge current: 7–9A, and pulse duration: 300s. Highlights • Magnetic field assisted EDM improve energy efficiency and environmental impact. • A thermo-physical model is proposed to calculate energy distribution of MF-EDM process. • Sustainable machining performance of EDM and MF-EDM are comparatively investigated. • The optimal parameter is: magnetic field intensity: 0.2T, current: 7∼9A, and pulse duration: 300μs. [ABSTRACT FROM AUTHOR]

Abstract Polycrystalline diamond (PCD) is one of the most important wear-resistant materials. Electrical discharge machining (EDM) is often used to remove pieces with different sizes, shapes, and surface qualities from polycrystalline diamond compacts (PDC) in order to satisfy the demands of PCD tools. However, as the special properties of the PCD, the structure transformation and removal process of the PCD materials are different to that of the cemented carbide substrate. This paper proposes a removal mechanism for PCD considering the morphology of discharge craters and the micro-structural evolution of diamonds. It was observed that the tensile residual stress was contributed to a large diameter value and irregular shapes of discharge craters in cobalt-rich areas. The graphene was obtained through the peeling process of graphite under the action of tensile residual stress when the thickness of metamorphic layer was in a small level. The degree of graphitization and number of crystal defects increased with increasing the thickness value of metamorphic layer according to the Raman shifted analysis. A metamorphic layer containing graphite, cobalt, and cobalt carbide was observed by the XRD analysis, which increased in thickness with increasing discharge energy. The hardness of PCD layer was reduced due to the action of the metamorphic layer, which damaged the performance of PCD tools. The electrical conductivity of the PCD layer was increased with increasing the thickness value of metamorphic layer, which contributed to the high machining efficiency with enlarging the discharge areas. Meanwhile, the diamonds were removed in the graphite form due to the graphitization of diamonds were the mainly removal mechanism in electrical discharge machining. Graphical abstract Unlabelled Image Highlights • The removal mechanism and micro-structural evolution of diamonds in EDM are proposed in this paper. • The diamonds were transformed into graphite before the diamonds were removed. • The thickness of metamorphic layer was key factor to a non-linear relationship between the amount of feed and machining time. [ABSTRACT FROM AUTHOR]

Abstract In micro-electrical discharge machining (micro-EDM), the minimum machinable size is determined by the material removal per pulse discharge. In this study, two types of single-crystal silicon tool electrodes with high electrical resistivity were used to fabricate the micro-rod by minimizing the material removal per pulse discharge, and to reduce the machinable size for micro-EDM. The EDM characteristics of micro-rods using silicon tool electrodes with high electrical resistivity were investigated. Based on the experimental results, it is found that the peak discharge current decreases with an increase in the electrical resistivity of the tool electrode. Consequently, the average diameter of discharge craters generated on the micro-rods is reduced to approximately 0.4 μm. The silicon tool electrode has also disadvantage of their higher tool wear ratio compared with that of copper, which is probably due to the brittleness of the silicon. Moreover, the material removal rate is significantly lower for the silicon tool electrodes compared with that for the copper tool electrode. Because the average diameter of the discharge craters generated by the silicon tool electrodes is small, an attempt is made in this study to fabricate a cemented tungsten carbide micro-rod with a diameter less than 1 μm using the silicon tool electrode with an electrical resistivity of 1.2 × 10−3 Ω m. The result is indeed promising since the diameter of the micro-rod is 0.8 μm, indicating that it is possible to fabricate micro-rods with a diameter within the sub-micrometer range by only using silicon tool electrode with high electrical resistivity in micro-EDM. Highlights • The peak discharge current decreases with an increase in the resistivity of the tool electrodes. • The diameter of discharge craters decreases by increasing the resistivity of the tool electrodes. • The tool wear ratio is higher for the silicon tool electrodes compared with that for copper. • The material removal rate is lower for the silicon tool electrodes compared with that for the copper tool electrode. • A cemented tungsten carbide micro-rod with a diameter of 0.8 μm is fabricated. [ABSTRACT FROM AUTHOR]

• Multi-physics coupling model considering practical boundary conditions was developed. • The effect of difficult forces acting on melt pool were analyzed. • The role of evaporation recoil pressure on material removal was revealed. • Melt pool dynamics and material removal were directly observed and analyzed under practical conditions. The melt pool dynamics and material removal mechanism in electrical discharge machining (EDM) is not clear yet. In this study, a thermo-hydraulic coupling simulation model considering practical boundary conditions was proposed to investigate the melt pool evolution and material removal on the anode in EDM, with the simulated results directly verified by the high-speed observation of the discharge process. Discharge currents of 5–15 A, a discharge duration of 10 µs, and workpieces of zinc and steel were used in the model, with the forces acting on the melt pool comprehensively integrated and their effects on the melt pool dynamics and material removal analyzed. The simulation results show that on the anode the evaporation recoil pressure is one of the dominant factors that drive the melt flow and cause the molten material removal. The increase of discharge current results in larger evaporation recoil pressure, and thus larger volume of the molten material is removed. Under the effect of evaporation, obvious fluctuation of the melt pool will occur. Meanwhile, the evaporation recoil pressure oscillates with the melt pool fluctuation, which may induce a wave-like motion of the molten material and promote the generation of debris particles. Novel high-speed observation methods were proposed to observe the melt pool evolution and the material removal, with the observed melt pool behavior consistent with the simulated results. The observation also shows that the intermittent removal of the molten material occurs in the case of long discharge duration, which is considered to be caused by the intermittent increase of the evaporation recoil pressure during the melt pool fluctuation. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is often used in the manufacturing of fatigue test coupons because it allows for the production of complex shapes and sharp starting notches. However, the effect that the machining process has on the corrosion susceptibility due to the surface alterations is unknown. This work focuses on the effect the machining method has on the corrosion and corrosion fatigue behavior of aluminum alloys. The study is aimed at understanding the influence of EDM processes on environmentally assisted cracking evaluations, namely crack growth rate. Conventional milling and electrical discharge machining were the machining process examined in this study; the machining parameters used were best practices for laboratory fatigue sample production. The following aluminum alloys (AA) 2024-T351, 5083-H116, 6061-T6 and 7075-T651 were evaluated in this study. EDM was performed using a 0.152 mm (0.006 in.) hard brass wire. Surface quality evaluations, microstructural analysis, electrochemical tests and corrosion fatigue testing in sodium chloride (NaCl) solution were completed. The study found corrosion rates are affected by the EDM machining in all aluminum alloys. In final testing, crack growth rate tests were completed in sodium chloride solution with starter notches that were traditionally cut and EDM machined for 7xxx and 2xxx series alloys. The testing showed accelerated fatigue crack growth rates for the samples with EDM notches as compared to cut notches. [ABSTRACT FROM AUTHOR]

In previous studies, the electrical discharge machining (EDM) ablation technology was developed, which removed materials by using the chemical energy released from the combustion of metal instead of the energy of pulse power supply used in EDM. Although the machining efficiency was greatly improved, the problem of recast layer that generated on the machined surface during EDM ablation process had not been solved. In this study, the combined process of EDM ablation and electrochemical machining (ECM) in aerosol dielectric was investigated, which aims to solve the recast layer problem of deep hole machining by using the aerosol dielectric EDM ablation technology. The mechanism was analyzed based on numerous experiments. Mechanism analysis indicated that the combined process includes the cycle machining state of micro-electrolysis and EDM ablation. Five microcosmic stages were included in the typical combined process: metal activation at discharge point, surface metal oxidation, blocking of surface metal oxidation, rapid oxidation of internal substrate metal, and micro-electrolysis of recast layer. Contrast experiments were performed to compare conventional electrical discharge machining, aerosol dielectric EDM ablation, and combined process of EDM ablation and ECM in aerosol dielectric. Results showed that the material removal rate of the combined process was 40% less than that of the EDM ablation but was still 3.7 times more than that of EDM. Moreover, the relative tool wear ratio decreased by 53.3%, the value of corner arc radius decreased by 44.3%, and the thickness of the recast layer decreased by 42.9%. [ABSTRACT FROM AUTHOR]

Recently, a multi-wire electrical discharge slicing (EDS) process has been proposed for slicing SiC ingots into wafers. A significant reduction in kerf loss is expected with this method compared with the conventional multi-wire saw method. However, this process entails a high risk of wire breakage. Therefore, in the present study, a novel electrical discharge slicing process utilizing a running ultra-thin foil tool electrode is demonstrated for the slicing of SiC ingots. Relative to multi-wire EDS, the risk of tool breakage can be reduced with this new technique by increasing the tool cross-sectional area. A 25-mm (1-inch) SiC ingot was successfully sliced with the proposed method and a kerf loss of about 100 μm was achieved by utilizing a foil tool electrode with a thickness of 50 μm. This paper summarizes the specific characteristics and results of this process, including the machining stability, machining strategy, selection of foil tool material and multiple simultaneous slicing. [ABSTRACT FROM AUTHOR]

The effective machining using the technology of wire electrical discharge machining (WEDM) is a compromise between cutting speed and resulting surface quality. The typical morphology of a machined surface using electrical erosion is characterised with numerous craters due to electrical discharges arising during the process of cutting. The study deals with the assessment of the influence of parameters of machine settings and material heat treatment on both quantitative and qualitative evaluations of craters on the surface of workpieces made of Ti-6Al-4V alloy. Using metallographic investigation, the diffusion subsurface phenomena occurring during the process of cutting on cross sections of preparations have been studied, and both qualitative and quantitative evaluations of the amount of electrode material stuck on the machined surface have been made. Diffusion processes occurring between the electrode and the cut material have been studied on cut surfaces as well as on cross sections using energy dispersive X-ray analysis (EDX). [ABSTRACT FROM AUTHOR]

Wire electrical discharge machining (WEDM) represents the effective technology of unconventional machining used for the manufacture of components with complex shapes, for machining of hard materials following heat treatment or of non-ferrous metals that are difficult to machine with conventional processes. One non-ferrous material is pure aluminium 99.5 which is used for this experiment: for the design of the experiment, machine parameters were setup for the fabrication of 33 samples aluminium 99.5. The objective of this study was to find the key parameters of machine setup for the manufacture of high-precision components with the required surface quality. For this purpose, an analysis of the morphology of the surface layer was made using electron microscopy (SEM), including a local analysis of the chemical composition (EDX). In addition, the surface topography using 3D profilometer and profile and area parameters of the surface quality were evaluated, including 3D colour filtered and unfiltered images of surfaces taken using light microscopy. The prepared metallographic preparations allowed an analysis of the sub-surface area, including a local chemical microanalysis of “recast layer” using EDX. This study discovered the optimal setting of machining parameters (gap voltage = 70 V, pulse on time = 6 µs, pulse off time = 50 µs, discharge current = 25 A and wire feed = 14 m·min −1 ) for the best quality of machined surface and the narrowest width of kerf for precision machining. [ABSTRACT FROM AUTHOR]

Alumina zirconia (ZTA) ceramics can be made electric discharge machinable by addition of a percolating network of an electrically conductive phase. In this study the influence of NbC content on the mechanical and electrical properties as well as the ED-machinability of ZTA-NbC ceramics containing 17 vol.% zirconia and 24–32 vol.% NbC were investigated. Samples were hot pressed from mixed and milled starting powders. Surface morphology and surface roughness of wire electrical discharge machined surfaces were studied by SEM and perthometry. Cutting speed was determined to benchmark the ED-machinability. Rising NbC contents progressively impede sinterability. Maximum strength, Young’s modulus and hardness were found at intermediate NbC contents. Conductivity evidently rises with NbC content, the cutting performance showed an adverse tendency. The surface quality of the materials was improved by increasing the content of conductive phase. Additional trimming operations can reduce the mean roughness of machined surfaces to 1 μm. [ABSTRACT FROM AUTHOR]

Wire Electric Discharge Machining (WEDM) is an unconventional machining technology using physical principles to cut materials. There are many factors affecting this process and having a fundamental influence on the final quality of the machined surface. Apart from the dielectric and wire electrode type used, these include, in particular, the machine setting parameters such as discharge current, gap voltage, pulse on and off time, and wire feed. Another very significant aspect of the machining process is mechanical and physical characteristics of the machined material including its heat treatment. This study deals with an analysis of morphology and topology of the surfaces of samples made of 4 structural materials and their 5 types of heat treatment. The analysis was carried out using electron microscopy (SEM) and a contact-less 3D profilometer which allowed evaluating the profile and surface parameters of surface quality including creating a 3D surface image. [ABSTRACT FROM AUTHOR]

In powder-mixed electrical discharge machining (PMEDM), a suspension of powder particles is added to the dielectric to achieve a high surface quality and to improve the material removal rate (MRR). However, for biomedical applications, the machined surface must be nontoxic and also contain bioactive species; these constraints limit the choice of powder material. This study focuses on machining orthopedic-implant materials based on titanium and titanium–tantalum alloys using bioactive hydroxyapatite (HA)-powder suspension as the dielectric. The influence of the powder particles and the work-piece composition on the machining performance was investigated. Employing a suspension dielectric with 5 g/L HA caused a smoother surface (Ra 2.1 μm) with a thinner recast layer (∼9 μm) as compared to using water to machine titanium which has surface roughness of Ra 2.4 μm with a recast layer close to 10 μm. In addition, the MRR of titanium machined in the HA-powder-suspension dielectric (6.4 × 10 −4 g min −1 ) was greatly lower than that in water (28.6 × 10 −4 g min −1 ). However, increasing the HA concentration led to a gradual increase in the MRR, electrode wear rate (EWR), surface roughness, and recast-layer thickness. The MRR, EWR, and the surface roughness of titanium and titanium–tantalum alloys under PMEDM exhibited an inverse relation with respect to the melting temperature and thermal conductivity of the alloy. Furthermore, calcium and phosphorus were incorporated into the recast layer, and their amounts decreased when the discharge current was increased. [ABSTRACT FROM AUTHOR]

The preparation of surface texture by EDM is considered as an effective method to improve the tribological properties of mechanical parts. In this study, a new water-in-oil (W/O) working fluid for the preparation of surface texture in EDM was developed, and a micro-pit array was prepared on AISI 1045 steel. The surface texture prepared with the water-in-oil working fluid exhibited high wear resistance performance. The analysis combined with the wear mechanism and mathematical model showed that the high wear resistance performance of the surface texture prepared by W/O working fluid was due to its good anti-deformation ability and efficient wear debris trapping ability. [Display omitted] • A new water-in-oil working fluid for preparing surface texture in EDM was developed. • The prepared surface texture exhibited high wear resistance performance. • The mathematical model of surface texture wear prepared in EDM was established. [ABSTRACT FROM AUTHOR]

A serious limitation of sink electrical discharge machining is the rapid geometric degeneration of sharp features due to localized wear. Electro-erosion edge honing is a novel process that creatively exploits this phenomenon for the edge preparation of cutting tools. This paper presents a geometric model of the process that can accurately predict the profiles of both symmetric and asymmetric edges that are prepared in the process. Numerical simulation of the model quantifies the concept of relative duty in the context of the process, and offers unique insights into process mechanisms. In particular, the critical influence of the wear ratio in determining the prepared edge being either rounded or chamfered is clarified, in consideration of the trajectory of successive discharge trains. The work further enables an understanding of the influence of initial edge defects on the processed edge, and presents guidelines for optimizing edge quality. [ABSTRACT FROM AUTHOR]

Electric discharge machining (EDM) is a widely-used non-traditional machining process in manufacturing of complicated structures based on localized thermal loads. Because of numerous difficulties in measuring temperature, no adequate knowledge on temperature distribution of workpiece, tool and plasma channel is available. On one hand, a large number of dispersedly-published papers have been reported so far to model the temperature distribution either analytically or numerically. On the other hand, an enormous amount of experimental attempt has been put into measuring the temperature by directly-measuring methods. In this study, a comprehensive review of analytical, numerical and experimental investigations on temperature prediction has been provided to organize different methods to integrate them as useful information for elucidating the differences between approaches and identifying their proximities to the real temperature distribution. This review also prepares a classification of the different methods of investigating temperature and provides an overview of some of the recent advances in this area to help researchers on selecting appropriate approaches among analytical, numerical and experimental techniques depends on applications and the availabilities of those techniques. The assumptions, limitations and features of different methods are described. Finally, the paper shows some required enhancements for EDM process to improve the total accuracy of temperature prediction as well as recommendations for future studies. [ABSTRACT FROM AUTHOR]

Single-crystal silicon carbide (SiC) is an important semiconductor material used in power electronics. Due to its high hardness and brittleness, SiC is very difficult to machine using mechanical methods. Electrical discharge machining (EDM) has recently garnered extensive research interest as a potential machining method for SiC. However, this technique induces severe subsurface damage on the workpiece. To date, mechanisms leading to EDM-induced subsurface damage in SiC have not been clarified. This study aims to investigate the atomic-scale subsurface damage in SiC induced by EDM using Raman spectroscopy and transmission electron microscopy (TEM). In cross-sectional TEM observations, three regions of subsurface damage were identified, namely, the re-solidified layers, heat-affected zones, and microcracks. It was found that SiC decomposed into silicon and carbon in the re-solidified layers, and the degree of decomposition depended on the discharge energy and workpiece polarity. The re-solidified layer was a mixture of crystalline/amorphous silicon, crystalline/amorphous carbon, and nano-crystalline SiC. The presence of an extremely thin graphite layer was observed in the re-solidified layer. The heat-affected zone remained crystalline but showed a different crystal structure distinct from that of the bulk. [ABSTRACT FROM AUTHOR]

High-speed electrical discharge machining (EDM) milling is investigated with working gap control. EDM milling has a merit that does not need complex electrode fabrication; however, it is necessary to improve the removal rate in EDM milling. Rotation of the electrode improves the removal rate, but this rotation causes a periodic change in the working voltage. As a consequence, the periodic change causes a disturbance that decreases the control performance. EDM milling realizes a high machining precision by the scanning method. A small working area allows for fast scanning. If the working gap is appropriate, it becomes longer because the machined surface of the workpiece is removed. Therefore, the conventional controller remains at the steady offset and lowers the machining efficiency. The proposed controller introduces a notch filter, which eliminates the frequency component due to rotation of the electrode. It also has a feed-forward compensator to eliminate the steady offset. The controller for each machining condition is derived from a coordinate transformation and the least-squares approximation. It is confirmed that the proposed controller achieves machining speeds that are 2–6 times faster in a straight line and greater than 30% higher in the profile machining than in the conventional one. [ABSTRACT FROM AUTHOR]

In micro electrical discharge machining (EDM), because the material removal per single pulse discharge mainly determines the minimum machinable size of a micro EDM, decreasing the material removal per single pulse discharge is important. In this study, in order to decrease the material removal per single pulse discharge, high electric resistance materials such as single-crystal silicon are used for electrodes. Analytical results show that when the electrode resistance increases, the peak value of the discharge current decreases, whereas the pulse duration increases. In addition, the discharge energy decreases when increasing the resistance. Silicon is used as a tool electrode, and the effect of resistivity of the silicon tool electrode on the diameter of discharge craters generated on the stainless steel workpiece is examined. Experimental results reveal that with increasing silicon electrode resistivity, the diameter of discharge craters decreases. Because the diameter of discharge craters can be decreased to 0.5 μm, improved finished surfaces of R z 0.03 μm are obtained. [ABSTRACT FROM AUTHOR]

Ti–6Al–4V alloy is widely used in many industries due to its outstanding properties. However, it has poor machinability using conventional mechanical cutting process. Electrical discharge machining is an alternative competitive process to machine titanium alloy by electrical erosion. This article studies the machining characteristics of Ti–6Al–4V with Cu–SiC composite electrode. Surface topography, subsurface microstructure, energy dispersive spectroscopy analysis, and micro-hardness have been analyzed. The machined surfaces show irregular compound structures, droplets of debris, shallow craters, and micro-pores. The surfaces processed by Cu–SiC electrode have fewer number of microcracks compared with that by Cu electrode. Continuous and uniform hardened layer can be achieved by Cu–SiC electrode. The hardened layer has significantly higher hardness than the bulk material because the new phases of TiC and TiSi 2 were created on the surface. [ABSTRACT FROM AUTHOR]

The efficient wire electric discharge machining (WEDM) technology is a trade-off between the cutting speed and the resulting surface quality. A typical morphology of a surface machined using WEDM contains a large number of craters caused by the electric sparks generated in the cutting process. The paper analyzes the influence of the cutting speed on the quantitative and qualitative evaluation of the craters formed on the surface of a workpiece made of the 16MnCr5 steel. Applying metallography to cross-section microscopic slides, diffusion subsurface damages were studied caused by the cutting. The diffusion processes taking place between the electrode and the material machined were studied using a local point EDX microanalysis applied both to the machined surfaces and to the cross sections. A detailed study was also carried out of the brass electrode to measure its wear rate caused by the cutting process as well as its degradation in terms of the quality of its morphology and the chemical composition of surface. [ABSTRACT FROM AUTHOR]

Electrical Discharge Machining (EDM) is a non-conventional machining process specially suitable for manufacturing hard-to-machine materials or geometrically complex parts. Many investigations have been presented combining EDM with ultrasonic (US) vibration of the electrode, but most of them have been intended to enhance the material removal rate of the process. In this paper US assisted EDM process has been used in order to improve the surface roughness in a finishing operation. For that purpose a copper rod tool electrode and a 1.2344 tempered alloy steel workpiece have been used. A pulsed US assisted EDM mode (PUEDM) has been developed and compared with the current EDM process and EDM assisted with continuous US vibration (UEDM). The results show that PUEDM process can improve the surface roughness and homogeneity of the machined surfaces in finishing EDM operations. [ABSTRACT FROM AUTHOR]

In this study, electrical discharge machining (EDM), a non-contact thermal machining process, is proposed for machining single crystal silicon carbide (SiC) which exhibits extreme mechanical hardness. However, as a semiconductor, SiC demonstrates significantly different EDM characteristics compared with those of metallic materials. This research clarifies the EDM characteristics of SiC from thermal, mechanical and chemical aspects through experimental and analytical approaches. The heat transfer analysis of a single discharge of SiC taking into account Joule heating effect revealed that Joule heating effect can increase the surface temperature of SiC near the discharge spot considerably. On the other hand, experimental investigations on the EDM of SiC found that brittle fractures along crystal orientations occur in the EDM of SiC due to thermal shock. However, the influence of the crystal anisotropy of SiC on the EDM characteristics was not significant. Finally, the EDM mechanism of SiC was investigated from chemical aspects. Oxidation reaction was confirmed in the EDM of SiC in deionized water. All of these factors helped improve the machining rate of SiC to a certain extent. [ABSTRACT FROM AUTHOR]

The tool electrode has a significant role in electrical discharge machining (EDM) performance, as it affects machining efficiency, surface quality and the geometrical accuracy of the machined component. This study presents a new approach for developing a pure copper electrode using severe plastic deformation (SPD) to enhance the machining characteristics during EDM. Equal channel angular pressing (ECAP) is selected because it is the most successful SPD method of processing bulk materials. Finite element analysis, microstructural assessment as well as nanoindentation tests are carried out to determine the behavior of pure copper after one and two ECAP passes. The effectiveness of EDM when using ECAP-treated electrodes is evaluated by introducing new techniques of measuring the volumetric overcut (VOC) and corner sharpness. In addition, tool wear rate (TWR), material removal rate (MRR), electrode wear ratio, surface roughness, surface crack density and the critical crack zone are studied. The results emphasize that an electrode subjected to one pass of ECAP can enhance the workpiece accuracy by decreasing the VOC and increasing corner sharpness by 13 and 66%, respectively. It is also revealed that the nanohardness enhancement following ECAP leads to lower TWR and electrode wear ratio. An investigation of the surface characteristics indicates a thinner recast layer is achieved when using one ECAP pass-treated electrode, which leads to 26% lower surface crack density. [ABSTRACT FROM AUTHOR]

WC-Co hard metals are materials widely used in wear applications, metal machining and highly fatigue loaded tools. Shaping tools and components made of hard metals often requires electrical discharge machining (EDM) that is well-known to negatively influence the material's fatigue properties. The current work demonstrates that it is possible to achieve a fatigue limit of electrical discharge machined specimens equal to the one of finely ground and polished reference samples. This is achieved by the application of advanced wire EDM technology combined with a sole surface post-treatment step of abrasive blasting. Stress amplitude-life curves were determined in a four point bending test setup. Depth profiles of residual stress were determined by means of X-ray diffraction for electrical discharge machined samples prior to and after blasting. Surface defect size was documented in metallographic cross sections by scanning electron microscopy. The surface residual stress state was found to be crucially important regarding the observed fatigue behavior. If the applied EMD technology produces cracks shallow enough to allow for their removal by abrasive blasting and compressive residual stress is introduced as deep into the surface as damage reaches, the negative effect of EDM on the fatigue limit is neutralized. [ABSTRACT FROM AUTHOR]

In this investigation, response surface method was used to predict and optimize the material removal rate and tool wear ratio during electrical discharge machining of AISI D6 tool steel. Pulse on time, pulse current, and voltage were considered as input process parameters. Furthermore, the analysis of variance was employed for checking the developed model results. The results revealed that higher values of pulse on time resulted in higher values of material removal rate and lower amounts of tool wear ratio. In addition, increasing the pulse current caused to higher amounts of both material removal rate and tool wear ratio. Moreover, the higher the input voltage, the lower the both material removal rate and tool wear ratio. The optimal condition to obtain a maximum of material removal rate and a minimum of tool wear rate was 40 μs, 14 A and 150 V, respectively for the pulse on time, pulse current and input voltage. [ABSTRACT FROM AUTHOR]

Surface modifications of titanium are widespread in an effort to improve the osseointegration capabilities of the metal for orthopaedic and dental applications. Here, electrical discharge machining (EDM) was used to create modified, notably, dual-topography surfaces on titanium. By swapping conventional copper electrodes for a titanium electrode and water dielectric, modified surfaces free of trace element contaminants were produced. Three surfaces were produced by varying the peak currents at 10 A, 29 A and a uniquely hierarchical multi-current combination of 29 A followed by 2.4 A. The physicochemical properties of these surfaces were analyzed by scanning electron microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), and Auger Spectroscopy. These revealed the topography of the modified surfaces and a titanium oxide layer that was markedly thicker on the EDM samples compared to controls. In vitro cell testing was carried out with osteoblast-like MC3T3-E1 cells. Cell differentiation was increased in all EDM modified surfaces compared to controls and early differentiation was promoted on the dual-topography surface. The present study suggests the promise of dual-topography surfaces created using EDM for implant applications. [ABSTRACT FROM AUTHOR]

Film cooling holes are required in many crucial and widely used structures. The creation of good film cooling holes requires machining at high speeds with high accuracy and good surface quality. For this purpose, a promising hybrid machining method combining electrical discharge machining and electrochemical machining, called tube-electrode high-speed electrochemical discharge drilling (TEHECDD), has been proposed, which can be used for machining difficult-to-machine superalloys. In TEHECDD, the flushing condition is considered as an important element. To improve the flushing condition and further enhance the machining performance, improved tube-electrode structures, obtained by varying the inner diameter and inner shape, are introduced. In this study, different inner structures are designed for the tube electrodes, whereby the mechanism of the enhanced TEHECDD performance for different tube-electrode inner shapes are analysed and the effects of different tube-electrode inner structures on the machining performance are investigated. The results show that an increase in the tube-electrode inner diameter results in a higher material removal rate, smaller average bore diameter, and smaller taper angle. However, for the single-hole tube electrode, a larger inner hole results in the formation of a residual cylinder. Thus, the double-hole and multi-hole tube electrodes are proposed and found to be effective in removing the residual cylinder. Finally, it is verified that the tube electrodes with improved inner shapes can be used to further enhance the machining performance. The double-hole tube electrode is confirmed to have the optimal structure. [ABSTRACT FROM AUTHOR]

Several composites of tetragonal zirconia polycrystals doped with 3 mol% yttria (3Y-TZP) and multiwalled carbon nanotubes (MWCNT) with concentrations from 0.5 to 4 wt% CNT were processed, spark plasma sintered, and characterised for a wide range of mechanical, electrical and thermal properties. In particular, a strong increase in electrical conductivity at room temperature was found with only 0.5 wt% CNT. However, the thermal conductivity was decreasing with increasing CNT content. Electrical discharge machining (EDM) using die sinking was carried out using the composites of 1 and 2 wt% CNT as workpieces. It was shown that both compositions could be successfully machined by EDM. The surface integrity and the subsurface were studied by SEM/FIB in order to determine the material removal mechanisms, which were found to be associated to spalling and melting/evaporation. Raman Spectroscopy was used to evaluate the damage of CNTs after EDM. [ABSTRACT FROM AUTHOR]