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Jet electrochemical milling (jet-EC milling) is a promising technique to machine hard-to-cut metallic materials with high machining efficiency and flexibility. The process of the jet-EC milling of Ti-6Al-4V Alloy is difficult to predict due to the interaction of multiple physical fields and the formation of passivation film. In this work, a novel model is established to simulate the jet-EC milling and predict machining profile. In this model, the interactional relationships among electric field, two-phase flow field, and geometry deformation are considered using a multiphysics approach, and the breakdown process of the passivation film is involved for accurately predicting the machining results. In addition, the passivation film breakdown process of Ti-6Al-4V alloy is studied experimentally. Finally, several experiments on the jet-EC milling of Ti-6Al-4V alloy are conducted to verify the simulation results and discuss the influence of the travel rate on the material dissolution. The current density distribution on the anode surface is clarified. The proposed model is more in line with the experiments. By applying an appropriate travel rate, a sharp edge is obtained without stray corrosion as the electrolyte forms an upward reflection and the un-machined surface is free from stray corrosion due to the absence of the electrolyte. [ABSTRACT FROM AUTHOR]

The (TiB + TiC)/TC4 composite is a new material with superior high-temperature resistance properties and structural strength. However, it cannot be easily machined by conventional methods. Electrochemical machining is an ideal method for the processing of titanium-matrix composites. In this study, the electrochemical properties of (TiB + TiC)/TC4 composites were investigated. The polarization curve of (TiB + TiC)/TC4 in a NaCl solution with a volume fraction of 20% was measured. The decomposition voltage was approximately 7.2 V. Basic electrochemical dissolution experiments were carried out on TC4 and (TiB + TiC)/TC4. The surface morphology was measured to investigate the dissolution mechanism. It was demonstrated that the reinforcing phase will fall off with the dissolution of TC4 and will not participate in the electrochemical dissolution reaction. Finally, electrochemical milling experiments on (TiB + TiC)/TC4 with different voltages and cathode feed rates were carried out to study the removal rate and surface roughness of the material. The material removal rate (MRR) increased, while the surface roughness decreased with the increases in the voltage and feed rate. A maximum MRR of 171.11 mm³ /min and minimum surface roughness of 4.281 μm were obtained at a voltage of 50 V with a feed rate of 20 mm min−1. [ABSTRACT FROM AUTHOR]

Stress-free polishing is the most potential machining method for high quality surfaces without surface defects. Traditional electrochemical polishing (L-ECP) is immersed in a liquid electrolyte to realize stress-free polishing. However, due to the limitation of its polishing principle, the electrochemical polishing process cannot improve the surface shape accuracy of the workpiece so far. In this work, a new method solid-liquid electrolyte electrochemical polishing (SL-ECP) for electrochemical polishing assisted by a solid electrolyte polishing pad is proposed. Power spectral density (PSD) of the profile of polished surfaces were compared, and it was found that the low-spatial-frequency error was reduced by contacting the flat solid electrolyte surface with the workpiece surface. After SL-ECP, the roughness Sa of the workpiece decreased from the initial 82.83 nm to 2.92 nm (10 μm × 10 μm), and the peak-to-valley value of the entire workpiece surface decreased from the initial 16.39 μm to 1.81 μm. And the material removal rate of SL-ECP was 35 times that of L-ECP using the same liquid electrolyte. This study not only proposes an efficient stress-free polishing method for high-quality surfaces, but also contributes to further understanding of the mechanism of electrochemical polishing [ABSTRACT FROM AUTHOR]

Interface between two immiscible electrolyte solutions (ITIES) is a powerful platform for chemical sensing and studying electron/ ion transfer reactions and is typically formed between the interface of two immiscible solutions such as an oil phase and an aqueous phase. Micro/nano ITIES interface are generally formed at the tip of a borosilicate/quartz pipette, inner surface of which can be rendered hydrophobic to be filled with an organic solvent by a method called silanization. Nano/micrometer-sized electrodes are typically silanized by vapor silanization methods in which silanizing agent in vapor phase is exposed to nanopipettes. Micrometersized pipettes have been also silanized by directly filling liquid silanization agent, one type of liquid silanization methods, but this method has not been used at the nanoscale. Liquid silanization method allows to selectively silanize a single channel in a dualchannel pipette platform. Here, we developed the liquid silanization method for nanoscale ITIES and demonstrated that a stable cyclic voltammogram for tetrabutylammonium ion transfer across water/dichloroethane interface can be accomplished. We also presented challenges for liquid silanization at the nanoscale and strategies to overcome them. The liquid silanization methods presented here lay the foundation for future development of dual channel multi-functional probe where one channel is nanoITIES. [ABSTRACT FROM AUTHOR]

The present study analyzes the efficient electrochemical dissolution of tungsten carbide-cobalt alloy (WC-Co) micro-tools for micromachining operations with an eco-friendly electrolyte. One of the essential factors in efficient anodic dissolution is the selection of appropriate electrolytes. Sulphuric acid (H2SO4) is extensively used in the electrochemical process to dissolve WC-Co due to its higher dissolution rate and efficiency. But toxicity of H2SO4, even at moderate concentration, poses a significant threat to the operator and the environment. Hence in this investigation, an eco-friendly electrolyte has been proposed which is a combination of sodium nitrate (NaNO3) and a complexing agent citric acid (C6H8O7), that not only gives a higher dissolution rate of WC-Co but also gives similar dissolution efficiency that of H2SO4. A detailed experimentation to optimize the concentration of complexing agent in the eco-friendly electrolyte was carried out through micro wire-electrochemical machining (micro-WECM) and was analyzed using yield parameters, topographical and material surface analysis as well as electrochemical analysis. This eco-friendly electrolyte produces higher dissolution rate and better surface finish in different levels of parameters in comparison to H2SO4. Potentiodynamic polarization test through linear sweep voltammetry (LSV) showed maximum current density for WC-Co alloy in the proposed eco-friendly electrolyte. [ABSTRACT FROM AUTHOR]

In this work, we target to isolate the SEI resistance of graphite electrodes in lithium-ion cells by impedance spectroscopy measured in blocking conditions (here = 0% SOC), where the charge transfer resistance RCT is significantly enlarged (~104 O cm² geom) and thus the corresponding semicircle shifted to very low frequencies. Therefore, we measure impedance spectra of graphite/LFP full cells with a gold-wire reference electrode (GWRE) in blocking conditions (graphite potential 2 V vs Li+/Li, 0% SOC) before and after formation. As electrolytes, we use LP57 (EC:EMC 3:7 + 1 M LiPF6) either without additive or with 1 wt% VC, 1 wt% FEC, or 1 wt% DiFEC as additive. By fitting the impedance data to a transmission line-based model, we show that the SEI resistance RSEI can be extracted from blocking condition impedance spectra, whereas SEI and charge transfer resistance are inseparable in non-blocking conditions. We validate our approach by determining the activation energies for the obtained ionic and SEI resistances. Finally, we introduce a potential-controlled cycling procedure which allows to assess RSEI during formation. Here, we show that SEI resistance evolution follows the electrolyte reduction potentials, which makes this method a useful tool to study film formation on Li-ion battery anodes. [ABSTRACT FROM AUTHOR]

The machining resolution of pulse electrochemical micromachining technology can be increased by shorting the pulse duration and changing the voltage signal waveform. With a triangular pulse, the energy per pulse was reduced by about two-thirds, and the machining gap was decreased by about eleven times compared to one with a rectangular pulse. Here, we put forward a real pulse waveform for electrochemical micro-machining. The pulse waveform is obtained by rectangular pulse plus differential circuits. The waveform can greatly reduce energy per pulse and surprisingly improve the precision of micro-electrochemical machining. The basic principle of the micromachining is analyzed. The equations of the machining accuracy and energy per pulse are deduced. Using the equations, the machining accuracy and energy per pulse as a function of the differential times of the differential circuits are calculated and compared with simulated and experimental results. Compared to the rectangular pulse, the energy per pulse for the waveform can be reduced by about six times and the machining gap was decreased can be improved by about 11 times. Using this method, some micro structures are produced and nanometer lever machining accuracy is realized which illustrates the proposed machining method. [ABSTRACT FROM AUTHOR]

The anodic dissolution of copper was investigated at a copper RDE in the Lewis acidic and basic composition regions of the roomtemperature AlCl3-EtMeImCl ionic liquid (IL) to assess the utility of chloroaluminate liquids as solvents for the electrochemical machining and electropolishing of copper. In the Lewis acidic IL (60 mol% AlCl3), the dissolution of Cu0 proceeds under mixed kinetic-mass transport control with an exchange current density of 7.00 mA cm−2 at 306 K and an apparent activation free energy of 19.7 kJ mol−1. A formal potential of 0.843 V was obtained for the Cu+/Cu0 reaction from potentiometric measurements. In the basic IL (< 50 mol% AlCl3), potentiometric measurements showed that the oxidation of Cu0 resulted in the formation of [CuCl2] −. In this case, the formal potential of the [CuCl2]−/Cu0 reaction is −0.412 V. At small positive overpotentials, the reaction exhibited mixed control and was first order in the chloride concentration, indicating that only a single Cl− is involved in the RDS. However, at more positive overpotentials, the reaction transitions to mass transport control, and a well-defined limiting current is observed for the anodization process. This limiting current scales linearly with the free chloride concentration in the IL. [ABSTRACT FROM AUTHOR]

Free of tool wear, residual stress, and surface damage, electrochemistry plays a significant role in precision machining. We report here a semiconductor polishing technique based on electrochemically induced chemical etching, in which the concentration distribution of electrogenerated etchant between the tool electrode and the semiconductor workpiece can be precisely controlled by the pulse frequency of the potential applied to the tool electrode. A theoretical model is established, and the finite element analysis shows that the concentration difference of the electrogenerated etchant at the peak and valley of the rough surface of the semiconductor workpiece is dependent on the frequency of the potential pulse. Consequently, the diffusion distance and concentration distribution of electrogenerated etchant at the tool electrode/electrolyte interface can be controlled effectively by tuning the frequency of pulse potential. Under a mechanical motion mode, the roughness of a raw GaAs workpiece can be reduced efficiently from 700 nm to 5.1 nm. This technique is ideal for the electrochemical polishing of semiconductor wafers. [ABSTRACT FROM AUTHOR]

Electrochemical micromachining (ECMM) is a promising and economical process that can machine hard-to-machine metals with high material removal rate and good surface integrity. In this work, an attempt has been made to develop a novel atomized electrolyte flushing technique to enhance mass transport. An atomizer is employed for supplying pressurized micro-droplets of electrolyte on the workpiece surface which leads to the formation of a thin and mobile fluid film. This thin film of electrolyte, moving with a high velocity helps in overcoming the problems associated with jet flushing such as radial overcut, stray corrosion, and usage of a large volume of electrolyte for machining. Numerical simulations of atomized electrolyte-based ECMM are carried out by considering a thin electrolyte film in the interelectrode gap to predict the evolution of anode profile on SS304 workpiece. Experimental observations suggest that in comparison with jet electrolyte flushing, the average dimple diameter reduced by 13% and the average dimple depth increased by 52.3% in case of atomized electrolyte flushing at an applied potential of 6 V and electrolyte conductivity of 1.5 S m−1. It is concluded that the consumption of electrolyte decreases significantly and the localization of dissolution zone improves which ultimately enhances machining performance [ABSTRACT FROM AUTHOR]

Tribocorrosion of passivating metals is a dynamic phenomenon causing degradation of materials by a combination of mechanical wear and electrochemical dissolution. The mechanical action typically produces a local removal of particles, metal as well as oxides, resulting in an exposure of the metal surface and is followed by a repassivation process, of which the time-dependent current response is a direct measure. Kinetics for interface-limited film growth were used to find an analytical expression for the current transients, including the conductivity of the electrolyte as well as the contribution from the confined geometry within the mechanical contact. The solution gave a good experimental fit to a series of experiments with a range of electrolyte conductivities, and also to correlate well with values obtained using electrochemical impedance spectroscopy. Parameters from the rubbing experiment were used to calculate curves that compared well with passivation transients recorded on a bare metal surface for the same electrolyte series. The evaluation procedure made it possible to assess the relative resistance contributions from the growing passive film, the confined mechanical contact geometry, and the electrolyte. [ABSTRACT FROM AUTHOR]

Many studies of Li-ion cells examine compositional changes to electrolyte and electrodes to determine desirable or undesirable reactions that affect cell performance. Cells involved in these studies typically have a limited test lifetime due to the resource intensive and time-consuming nature of these experiments. Here, electrolyte and electrode analyses were performed on a large matrix of cells tested at various conditions and with various cycle lifetimes. The matrix included LiNi0.5Mn0.3Co0.2O2 (NMC532)/graphite and LiNi0.6Mn0.2Co0.2O2 (NMC622)/graphite pouch cells with excellent performing electrolyte mixtures, both cycling and storage protocols at 40 °C and 55 °C with both 4.3 V and 4.4 V upper cutoff potentials. This study presents post-test analysis (electrochemical impedance spectroscopy, differential voltage analysis, differential thermal analysis), electrolyte analysis (gas chromatography, quantitative nuclear magnetic resonance), and electrode analysis (micro X-ray fluorescence) for these cells after 3, 6, 9, and 12 months of testing. Many products and reactants, such as fraction of transesterification, gas production, transition metal dissolution appeared to have a constant rate of increase in this 12-month observation period. In most cases, results from cells after 3 to 6 months of testing could be used to reasonably estimate the status of the cells (electrolyte composition, gas production, transition metal dissolution) at 12 months. [ABSTRACT FROM AUTHOR]

Electrochemical discharge machining (ECDM) utilizes the principle of thermal melting and chemical dissolution for machining "non-conductive" materials like ceramics, glass, silicon wafers. These materials exhibit colossal applications in the fields of MEMS and lab-on-chips. Since its first demonstration, different aspects of the ECDM process have been studied for improving its efficiency. However, only a few numbers of studies were delineated to comprehend the mechanism of gas film and effective parameters for its stability concerning the machining repeatability. This paper comprehensively reviews the gas film mechanism concentrating on bubble formation, bubble adherence, bubble amalgamation, departure and breakdown behavior. The parameters for controlling the gas film stability such as voltage, current, gas film formation time, gas film thickness, surface tension, viscosity, surface topography, magnetic field, tool electrode's motions and material, are also likewise discussed. Moreover, research findings on ECDM performance based on discrete input parameters is also covered and presented. It was concluded that stabilized gas film significantly influences machining efficacy and can be achieved effectively by controlling the electrolyte's electrochemical properties, tool electrode shape and motions. Further, the paper underlines the future possibilities that may have the potential to enhance the ECDM performance. [ABSTRACT FROM AUTHOR]

Hybrid laser-electrochemical micromachining is a fast and force-free processing technique to machine difficult-to-cut multimaterials with conductivity variations and has the advantage of accelerated material dissolution, oxide layer weakening and surface quality. In this process, the laser can assist electrochemical dissolution or participate in material removal depending on the fluence available on the workpiece surface. The tool-based configuration allows delivery of laser and ECM at higher machining depths and achieves homogeneous application of the two aforementioned processes. The combination of laser and ECM results in high material removal, better surface integrity and processing of advanced materials. On passivating materials, the oxide formation is weakened. In this research, a multidisciplinary model scheme is proposed using a global modelling approach where the model mimics several microscopic physical and chemical phenomena involved in this tool-based hybrid laser-ECM process. The model takes into account electric currents, fluid dynamics, modelling of laser source, hydrogen and oxygen gas generation and heat transfer in solids and fluids. The model allows to study temperature effects on each of the phenomena in the model. Material removal is simulated by using a deformed geometry feature and an automatic remeshing technique generates a new boundary for each subsequent solution step on Comsol® multiphysics platform. The multiphysics model is presented in detail with a brief description and intuitive explanation of each physics module. The proposed multidisciplinary model scheme can improve the physical understanding of the hybrid laser-ECM process as well as assist in process design for specific applications. The model allows to predict the machined profiles and current density distribution simultaneously. This model also provides insights into several multiphysics phenomena occurring in the interelectrode gap which are difficult to characterize experimentally and therefore the model can act as a virtual sensor. In the later sections of this paper, model based findings are supported experimentally. [ABSTRACT FROM AUTHOR]

The production of economical turbine slots with high efficiency and good surface integrity is a common concern in aviation manufacturing. State-of-the-art wire electrochemical machining (WECM) cannot afford the efficient precision machining of macro structures with thicknesses over tens of millimeters. This work investigated a pulse-current WECM process combining high-speed rotation of a helical wire tool and axial electrolyte flushing. Theoretical analysis and experimental results indicate that pulse frequency has a significant influence on the machining of thick specimens. The pulse-current charging process was prolonged with the increase in workpiece thickness, and it took up the majority of the pulse-on time at a pulse frequency over 50 kHz when the workpiece thickness reached 15 mm. The maximum feed rate first increased with pulse frequency, and then decreased from 20 to 100 kHz when a 20-mm-thick workpiece was being cut. Subsequently, the processes of electrolyte refreshment and product removal were maximized when the helical wire electrode rotated clockwise, and axial electrolyte flushing was applied. Finally, a fir-tree slot of 20 mm thickness with good dimensional consistency and good surface quality was stably processed at a rate of 5 μm s-1 . [ABSTRACT FROM AUTHOR]

Passivating electrolyte and pulse power supply are usually adopted in micro electrochemical machining (ECM). For Fe–Cr–Ni based alloys, metal oxides generate and cause significant passivation effects. Meanwhile, with short pulse-on time (Ton), current densities are time-dependent. These passivation and transient effects are beneficial to improved machining localization, but they also result in very slow metal dissolution and even suspension of micro ECM processes. To further reveal the micro ECM mechanism, the electrochemical behavior of Fe–Cr–Ni based alloys was investigated. The equivalent circuit was proposed to represent passivation and transient effects, while resistances (Rox, Rdis) represent metal oxidation and metal dissolution reactions, and capacitance (C) represents the double layer. The material removal rate (MRR) was calculated from circuit elements and processing parameters. Electrolyte constituent and Ton were deduced as the main influencing factors. Taking 18CrNi8 steel as a case verification, specific circuit elements were analyzed by chronoamperometry tests. MRRs with different electrolytes and Ton were quantitatively predicted. The experimental effects of electrolyte and Ton on MRR agree with the predicted results. Therefore, the equivalent circuit is a practical approach to representing the electrochemical behavior of Fe–Cr–Ni based alloys. Combined with circuit elements analysis, the MRR can be predicted and improved. [ABSTRACT FROM AUTHOR]

Sensing materials play a key role in the successful implementation of electrochemical sensors, and nanotechnology has emerged as an important and rapidly growing field for stimulating the innovation of high-performance sensors. The fabrication, characterization, and evaluation of the nanostructured electrodes are therefore a focus of this field. Compared to a variety of dry and wet technologies which have been extensively developed for this purpose, electrochemical methods are typically convenient, highly effective, and potentially low-cost for the production of different nanostructures. This mini review is designed to introduce a unique electrochemical method - electrolytic metal-atom enabled manufacturing (EM²) and its application in electrochemical sensors. The EM² technique employs electrolytic metal atoms generated from their corresponding salt precursor as a tool to nanostructure a wide range of substrate electrodes used in electrochemical sensors, based on a one-pot electrochemical deposition and dissolution of the metal atoms in the same electrolyte bath. Briefly, the metal atoms are electrodeposited on a substrate electrode during the cathode reduction, and they are selectively removed from the substrate during the subsequent anode oxidation. Because of the interactions between the electrolytic metal atoms and the substrate atoms, the repetitive electrodeposition and dissolution of the former on the substrate enable the nanostructuration of the substrate, particularly within its surface layers. The nanostructured electrodes have demonstrated very attractive performance for the determination of numerous analytes, such as high sensitivity and selectivity, high interference tolerance, and low detection limits. However, the EM² technique and the application of the resulting nanostructured electrodes in electrochemical sensors and beyond have still been very limitedly investigated. In order to bring the community from academic, industries, agencies, and customers together to develop the EM² technique and advance electrochemical sensor systems, this mini review will introduce the thermodynamic and kinetic fundamentals of this technique, the characterization of resulting nanostructures, the analysis of their electrochemical behavior, and the implementation of this technique for the development of advanced sensor electrodes. Finally, an outlook with a focus on further research areas is provided. [ABSTRACT FROM AUTHOR]

The micro size and mechanical properties of carbon fiber make it an ideal electrode material, but the low surface area of carbon fiber promotes a poor electrochemical response. The combination of graphene quantum dots and metal oxide may modulate their chemical and electrochemical properties, resulting in synergistic signal amplification effect. In this study, a new robust nano-hybrid microelectrode was designed by modifying carbon fiber with boron-doped graphene quantum dots/ZnO nanorod for the electrocatalytic analysis of hydroquinone (HQ). Remarkably, high specific surface area of vertically-aligned ZnO nanorod promoted loading of high-density boron-doped graphene quantum dots. Electrochemical results showed that these modifications promoted a larger active surface area and electron transfer of the carbon fiber microelectrode, as well as enhancement of the electrocatalytic activity toward HQ. Under optimal conditions, the linear response range of the proposed microelectrode to HQ was 0.1 to 100 µM, and the limit of detection was 0.03 µM. The proposed microelectrodes show good repeatability, reproducibility and electrode stability. Furthermore, the proposed microelectrode was successfully applied to environmental water samples analysis of HQ, providing a new method for the efficient detection of HQ. [ABSTRACT FROM AUTHOR]

Microgrooves used in microelectromechanical systems (MEMS) are small, precise and usually made of hard-to-machine material, whose surface roughness significantly affects their performance and service life. Wire electrochemical micromachining (WECMM) has been used to machine them. Sometimes, it takes extra time to polish the microgrooves produced by WECMM when they couldn't meet the requirement of some special products in terms of surface quality. In this study, a new method is proposed to produce high quality surface efficiently that simultaneously implements electrochemical cutting and polishing in phosphoric acid (H3PO4). Ethanol, which has a lower density than water, was added to the electrolyte to improve mass transport and the flatness of the microgrooves. The polarization curves were measured to explain the principle of WECMM in H3PO4 solution. The effects of the composition of the electrolyte and machining parameters on curvature and surface roughness were studied theoretically and experimentally. In optimal conditions, a microgroove with a surface roughness of Sa = 0.039µm and Ra = 0.033µm was obtained. [ABSTRACT FROM AUTHOR]

To address the issues of the existing laser and electrochemical machining (LECM) processes in controlling the machining precision, machining depth limit, and taper angle, a novel LECM based on internal total reflection (LECM-ITR) has been proposed. In LECM-ITR, both the electrolyte jet and laser beam were guided and transferred to the machining area, synchronously. Since the tube electrode could feed into the workpiece, the laser could act on the high depth machining area with less laser attenuation. The materials could be removed by using laser-materials interaction and electrochemical dissolution. Small holes with depth of 2mmhave been processed on aluminum alloy and stainless-steel workpiece successfully. Experimental results showed that LECM-ITR could decrease the side gap by 23.6%, reduce the taper angle by 60.8%, and improve materials removal rate by 118.8%. The mechanism of materials removal rate and precision enhancement by LECM-ITR were discussed, including (1) Laser induced temperature rise at the machining area could improve the machining efficiency of ECM with the increased electric current density; (2) The formed anodic oxide layer in larger thickness could enhance the machining precision of ECM with increasing time constant of the electric double layer at the machining area. [ABSTRACT FROM AUTHOR]

In counter-rotating electrochemical machining, the current density at a certain point on the workpiece surface presents a pulse characteristic due to the rotation of the workpiece. The waveform and the period of the current for material dissolution are different from that in conventional pulse ECM, resulting in different dissolution performances. In this paper, the pulsating dissolution behaviors of nickel in rotating processes are investigated. Nickel sheets are particularly used to investigate the dissolution processes during one rotation cycle and at different rotational speeds. The machined nickel surfaces are examined by using scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The results indicate that the pulsating dissolution of nickel depends strongly on the rotational speed. Passivation, pitting, high rate dissolution and selective dissolution occur successively during one cycle at low rotational speeds. While, when the rotational speed is over 50 rpm, passivation and pitting alternately happen due to the shortening of the pulse period, which results in rapid decrease in material removal weight. Based on the above research, it can be concluded that the low rotational speeds are more favorable for the effective machining of nickel in CRECM. [ABSTRACT FROM AUTHOR]

Ti-48Al-2Cr-2Nb alloy has received considerable attention because of its high-performance applications in the aerospace industries. With high strength and stiffness, Ti-48Al-2Cr-2Nb has a density only half that of nickel-based superalloy. Electrochemical machining is suitable for processing of such alloys. This study focuses on the electrochemical dissolution behavior of extruded and casted Ti- 48Al-2Cr-2Nb in NaNO3 solution. The dissolution mechanisms of extruded and casted Ti-48Al-2Cr-2Nb are revealed. The open circuit potentials, polarization curves, and material removal rate of extruded and casted Ti-48Al-2Cr-2Nb are compared. The results indicate that both show similar polarization behavior, but extruded Ti-48Al-2Cr-2Nb has a higher material removal rate. Dissolution experiments carried out at different current densities and corrosion times show that the dissolution morphologies of extruded and casted Ti-48Al-2Cr-2Nb are significantly different. The former shows a gully-like dissolved morphology, but the lamellar colonies of the latter are fully exposed, and there is severe intergranular corrosion at low current density. With an increase of the current density, extruded Ti-48Al-2Cr-2Nb shows better surface quality. It was found that the lamellar plays an important role in electrochemical dissolution behavior. Electrochemical dissolution models of casted and extruded Ti-48Al-2Cr-2Nb are proposed. [ABSTRACT FROM AUTHOR]

Wire electrochemical machining(WECM)is a recently introduced fabrication processwhich is yet to be fully investigated. Preliminary studies have shown that it offers superior feasibility and capability concerning the fabrication of various microfeatures. More extensive investigations are needed to discover any associated problems with the process and to extend its applicability and efficiency by determining its limitations in order to make this process a successful fabrication technique not only in microdomains but also for macro fabrications as well. Here we begin with a detailed overview of the fundamental and technological aspects of the WECM process. We then discuss its mass transfer strategies and kinematics, which are equally important as associated operating parameters, as well as the apparatus, materials, and machining conditions, challenges, and applications. Finally, we note recent advances to guide upcoming research attempts and future investigations aimed at making this anodic dissolution process proficient and established. [ABSTRACT FROM AUTHOR]

Wire electrochemical micro machining (WEMM) using ultra-short pulses has been recognized as a flexible and effective tool for producing planar contour micro-features. However, high-efficiency mass transport in the extremely narrow machining gap (several micrometers or even smaller) is still a great challenge. Here, a method of WEMM assisted with coupling axial and intermittent feed-direction vibrations is proposed. The mechanism of the mass transport in the machining gap using this method was theoretically analyzed with the results indicating that the proposed method was very beneficial for improving the mass transport rate in the machining gap, owing to the high flow velocity in both the feeding and axial directions. A series of comparative experiments with different vibration styles were performed, the results of which were in accord with those of the theoretical analysis. Then, the effect of wire feed length, traveling speed, and amplitude for the intermittent feed-direction vibration to the machining efficiency and quality was investigated. Finally, under one group of optimal machining conditions, a multi-slit micro-structure with small standard deviation (about 0.53 µm) of slit width (about 13.8 µm) and good surface roughness (about Ra = 0.042 µm) was successfully fabricated using a wire electrode with the diameter of 10 µm. [ABSTRACT FROM AUTHOR]

In the past decades, wire electrochemical machining (Wire-ECM) has been extensively investigated for machining flat surfaces on varying engineering materials. In the present work, an attempt has been made to develop a novel technique (mask-less as well as through-mask) for generating macro as well as micro thread profiles on cylindrical rotating shafts using wire electrochemical turning process (Wire-ECTrg). Profiles with rounded edges like British Standard Whitworth (BSW) thread profile (Thread angle 55°) are fabricated using the mask-less method. Typical thread profiles are characterized and the impact of various input parameters on two key profile features, thread depth and thread angle are investigated. Generation of ball-full radius thread profile is very cumbersome to make through conventional turning process as it also requires a complex profiled tool. This type of thread profile is machined using the through-mask method. Three different engineering materials namely, copper, stainless steel 304 and a bio-compatible alloy of titanium Ti-6Al-4V are adapted for generating different thread profiles to show the versatility and applicability of the proposed technique. A ball-full radius thread of pitch 450 μm on stainless steel 304 is successfully fabricated using a single pass through-mask wire electrochemical turning process with an average percent error in groove radius of 2.42%. [ABSTRACT FROM AUTHOR]

In electrochemical micromachining using ultrashort pulses, pulse duration is the only effective parameter for controlling machining resolution. In this study, a controlled electrochemical micromachining technique was proposed. An adjustable capacitance element was included in an equivalent circuit of electrochemical micromachining to form a coupled fluid-electric circuit. The time constant of the coupled fluid-electric circuit depended on both local separation between electrodes and the adjustable capacitance. Therefore, the adjustable capacitance could be utilized as another control parameter of machining resolution.With an increase in the capacitance, a large polarization voltage can be easily confined to electrode regions in very close proximity. This technique was used for the local etching of some microstructures, and a nanoscale machining resolution was achieved. [ABSTRACT FROM AUTHOR]

In electrochemical machining (ECM), the machining accuracy is to a great extent affected by the stray corrosion at low current density. In this paper, an electrodeposited nickel film is used to localize the anodic dissolution of Inconel 718 in counter-rotating ECM (CRECM). The anodic dissolution behavior of nickel in NaNO3solution is investigated by linear sweep voltammetry, cyclic voltammetry, and dissolution efficiency measurement, and the surface evolution process is monitored by using a charge-coupled device. The results indicate that nickel is a favorable material with desired passivation characteristic that can be used for the localization of anodic dissolution of Inconel 718 in CRECM. The cylindrical Inconel 718 workpiece is covered by a thin nickel film, and is tested in the CRECM experiment. The experimental results show that the electrodeposited nickel film on the cylindrical surface can be rapidly dissolved under high current density. In contrast, the nickel film on the low-current-density area can be well reserved, and thereby protect the surface of the convex structure from stray corrosion. As a result, the anodic dissolution of Inconel 718 is located merely in the high-current-density region, and the surface quality and the profile of the convex structure are significantly improved. [ABSTRACT FROM AUTHOR]

Newly developed wire electrochemical machining (WECM) operates in the same principle of electrochemical machining (ECM) and has recently been very popular for fabrication of different microfeatures effectively. However, the capability and possibility of this newer process is still out of limelight and require specific and extensive research to explore. Hence, the present research work deals with indigenous development of suitable WECM setup for fabricating microslits with feed values as high as that employed during wire electrical discharge machining (WEDM) process, thereby making WECM a cost effective technique for batch scale production. The influence of applied voltage and duty ratio on maximum feed has been investigated and mathematical modeling for finding out a correlation between maximum feed with values of voltage and duty ratio has been developed and validated. Moreover, maximum feed achieved with different parameter settings has been tabulated. It has been found that maximum feed that can be achieved during controlled machining with 18 V, 18% duty ratio, 50 kHz frequency and 0.1 M H2SO4 is 0.84375 mm/min which can still be compared with feed rates commonly employed during WEDM, given the fact that tungsten wire of diameter as low as 50 μm has been used in the present study. [ABSTRACT FROM AUTHOR]

Laser rapid forming (LRF) is a newly developed method of additive manufacturing that has drawn much attention owing to its outstanding advantages. However, direct formation of components with high precision and high surface quality through LRF is extremely time-consuming and expensive. To address this problem, electrochemical machining (ECM) was introduced as a subsequent finishing process. In this paper, electrochemical machining property of the laser rapid formed (LRFed) Inconel 718 alloy (both as-deposited and solution-annealed) was studied. On as-deposited LRFed sample, polarization behavior and current efficiency show isotropy, despite the anisotropy of the microstructure. After a solution annealing treatment, the polarization behavior shows no difference, but the material will be more difficult to machine. The surface topography after ECM shows anisotropy on as-deposited LRFed sample, and dendrites as a microscopic structure and layer-band (on vertical sections) as a macroscopic structure are noticeable. The height of layer bands and surface roughness (Ra) decrease with increasing current density. On solution-annealed sample, the dissolved surface was smooth and no subgrain boundaries or layer bands were observed. Finally, deep-small hole, grooves and flat surfaces were produced successfully through ECM. [ABSTRACT FROM AUTHOR]

Electro chemical discharge machining (ECDM) is a hybrid machining process. This process has potential application for micro fabrication in nonconductive work materials such as glass. Micro fabricated holes and channels on glass are widely used in micro electro mechanical systems and bio medical devices. ECDM process takes place in an electrolytic cell consisting electrolyte upto certain level above workpiece. This electrolyte level affects the machining efficiency and quality of fabricated micro hole or channel. In this article, the electrolyte level was varied from 0.1 to 4 mm to investigate the effect on process responses of ECDM during fabrication of micro hole in glass. The process responses were material removal rate, depth of cut, heat affected zone and overcut. The effect of electrolyte level was characterized by spark discharge on voltage time wave form and microscopic images. The results revealed that an optimal value of electrolyte level is required for precise machining. [ABSTRACT FROM AUTHOR]

The bulk glass-forming alloys Zr59T3Cu20Al10Ni8, Zr57Cu15.4Al10Ni12.6Nb5 and Zr55Cu30Al10Ni5 were fundamentally analyzed regarding their anodic reactivity in 250 g/L NaNO3 solution - a standard electrolyte for electrochemical (micro)machining. All alloys exhibited stable passivity in a wide potential range. At potentials >2 V vs. SCE (saturated calomel electrode) a sharp breakdown of the passive state and active dissolution occur. By controlled electrolyte flow the transpassive reaction rate can be enhanced. Re-passivation from the transpassive state is not spontaneous - it requires a wider potential or time window. The influence of alloy composition and structural state will be discussed as well as consequences for the machining process. [ABSTRACT FROM AUTHOR]