Electrochemical Machining Research Articles

Optimization and experimental study on cathode structure of electrochemical machining titanium alloy inner helix

Optimization and experimental study on cathode structure of electrochemical machining titanium alloy inner helix

Electrical discharge and electrochemical hybrid sinking machining using water-in-oil nanoemulsion

Electrical discharge and electrochemical hybrid sinking machining using water-in-oil nanoemulsion

Estimation of Battery State of Charge Based on Electrochemical Impedance Spectroscopy and Machine Learning

With the increasing application of lithium-ion batteries in energy storage (ES) and electric vehicles (EV), the operation state and the safety early warning are particularly important. Due to the complexity of lithium-ion batteries, predicting the state of charge (SOC) of batteries is still a great challenge. In this paper, an electrochemical impedance spectroscopy (EIS) based on the SOC estimation method was proposed. The EIS of different SOC under 25℃ was measured, and the variation characteristics of EIS were summarized from the aspects of amplitude and phase by using the full band information. Finally, the linear system and BP neural network model were constructed by selecting the characteristic parameters at a specific frequency. The results demonstrate that the prediction effect of the BP neural network is better, and the error is found to be less than 3%.

Improvement on surface quality of Inconel-718 slits via laser cutting and wire electrochemical machining processes

In the paper, we present a combined gas–assisted laser machining and wire electrochemical machining (W-ECM) process to improve the surface quality of slits produced in Inconel-718, a high-strength nickel-based alloy widely used in aircraft engine parts. First, a laser cutting was applied to produce the slit structure in Inconel-718, where the power and feed rate were varied to identify the optimal processing parameters. Subsequently, the slits were processed by a custom-developed W-ECM process. The results were evaluated by characterizing the surface roughness and kerf width of the slits. Through this combined approach, a 90% average improvement on surface finish was achieved with a 10% increase in kerf width. In addition, the typical striation marks and thermal damages from laser machining processes were entirely eliminated in all slits. The new process is precise and low-cost, which may find important applications in high-precision laser machining applications.

Jet engine blade: Design, material, and manufacturing

The engine is the most important part of an airplane. Since the blades of an engine are a major factor in jet engine performance, the research of engine blades has always been a hot topic in the field of aerospace. This paper summarizes the research status in the field of jet engine blades. As for the design of the jet engine blade, the design of aerofoil and the geometrical structure of the engine blade is introduced. In the material selection of engine blades, titanium alloy materials, and the application of composite materials are introduced. Electrochemical machining (ECM) and additive technology of engine blades are introduced. The differences between them and traditional casting techniques are compared. The comprehensive analysis shows that the research on engine blades is becoming more and more mature, but there are some challenges in further optimization of manufacturing technology and materials. This paper may offer a reference for the design of jet engine blade.

Fabrication of Dimples by Jet-ECM of Zr-Based Bulk Metallic Glasses with NaCl-Ethylene Glycol Electrolyte.

Zr-based bulk metallic glasses (BMGs) possess unique mechanical and biochemical properties, which have been widely noticed. Jet electrochemical machining (jet-ECM), characterized by a high-speed jet, is a non-contact subtractive method with a high resolution and a high material removal rate (MRR). Past work on the electropolishing of Zr-based BMGs has indicated the feasibility of the NaCl-Ethylene Glycol (EG) electrolyte. In this research, the jet-ECM of Zr-based BMGs in the NaCl-EG electrolyte was studied to explore the dissolving mechanisms and surface integrity according to the voltage, pulse-on time and effective voltage time. The diameter, depth and surface morphologies of dimples were evaluated. The results showed that using this alcohol-based electrolyte led to a desirable surface morphology. The diameter and depth of the dimples varied with the voltage and the effective voltage time in a significantly positive proportional manner. Additionally, cases based on multiple parameter sets exhibited different stray corrosion severity. Afterward, machining performance can be enhanced in the next stage by tuning machining parameters to obtain microscale dimples with better quality.

Comparison of electrochemical dissolution properties of Hastelloy X in NaCl and NaNO3 solutions

The electrochemical dissolution properties of Hastelloy X are of great significance to its electrochemical machining (ECM). This study focuses on the electrochemical dissolution properties of Hastelloy X in NaCl and NaNO3 solutions. The open circuit potential, polarization curve, electrochemical impedance spectroscopy (EIS) and current efficiency were investigated, and the dissolution mechanisms were revealed. The results revealed that the breakdown potential and electrochemical impedance in NaCl solution were smaller than that in NaNO3 solution, confirming that oxide film was broken more easily in NaCl solution. Local pits and many electrochemical products were observed on the surface, which were formed by electrochemical dissolution, and the main composition of products was the hydroxide and oxide. With the increase of current densities, the current efficiency increased in NaCl solution, while decreased in NaNO3 solution. The current efficiency values and surface roughness demonstrated that at high current density, the rate of electrochemical dissolution was higher in NaCl solution, but better surface quality can be obtained in NaNO3 solution. The research can provide valuable theoretical guidance for the ECM of aerospace parts related to Hastelloy X.

Ultrasonic Vibration-assisted Electrochemical Discharge Machining of Quartz Wafer Micro-Hole Arrays

The micro-hole machining of quartz wafers depends on photolithography techniques akin to those used in semiconductor fabrication. These methods present challenges due to high equipment setup costs, large space requirements, and environmental pollution risks. This research applies ultrasonic vibration assistance in electrochemical discharge machining to create an array of micro-holes on quartz wafers. In the experiments, a self-prepared tungsten carbide micro-electrode array served as the tool electrode. This electrode was a 2 × 2 square array, with needles measuring 30 × 30 μm. A series of experiments was conducted to investigate the effects of various machining parameters, including working voltage, feed rate, duration time, duty factor, and ultrasonic power level, on the characteristics of the micro-hole array. The characteristics included average hole diameter and through-hole surface morphology. The experimental objective was to achieve a through-hole diameter of 80 μm with an accuracy of ±8 μm. During the electrochemical discharge machining, suitable ultrasonic vibrations can thin the insulating gas film coating on the electrode surface, resulting in a more uniform gas film. As the insulating gas film’s thickness decreased, so did the critical voltage needed for the electrochemical discharge machining, reducing the hole’s diameter expansion. The ultrasonic vibration assistance can enable the satisfaction of the dimensional accuracy requirement. The experimental results indicate that ultrasonic vibration assistance can effectively improve the processing capacity and reduce sample fragmentation. A working voltage of 44 V, feed rate of 1 μm/6 s, duration time of 30 μs, duty factor of 30%, and ultrasonic power level of 1 resulted in better inlet and outlet surface morphology without outlet fragmentation. Moreover, the average diameters of the inlet and outlet were roughly 80 μm while meeting the through-hole diameter of 80 μm with accuracy of ±8 μm.

Discharge Characteristics and Mechanisms of Electrolytic Discharge Processing by Jet Mask

As a novel microfabrication method, electrochemical discharge machining has remarkable effects on the forming and processing of brittle and hard materials and non-conductive materials, but little research has been done on the electrochemical discharge mode in the jet state. To fulfil the potential of this technology, innovative research on the discharge characteristics and mechanism of electrochemical discharge machining in the jet mask is proposed. A high-speed camera observation experiment was set up to record the process of the jet flow column discharge formation and penetration. Changes in the electric field of the electrolytic jet channel were analysed by simulation software, and the morphology of the machined micro-pits was observed using a microscope. A mathematical derivation of the dielectric electric field in the gas–liquid two-phase jet column reveals the mechanism of discharge channel formation in the jet state. The experiments show that when the processing voltage is 400 V, a stable continuous spark appears, realizing the unique characteristics of a large-gap long-distance discharge and a flat small circle-shaped discharge mark produced at the bottom of the crater. The actual field strength within the bubble of this model obtained by mathematical derivation is approximately 61.5 kV/cm greater than the critical field strength for air bubble breakdown in the standard state, where bubble breakdown occurs in the discharge.

High-efficient and scalable fabrication of robust superhydrophobic microarrays through maskless electrochemical machining

Superhydrophobic microarrays have shown great promise across various domains such as droplet manipulation, anti-icing, oil-water separation, and drag reduction. Nevertheless, the efficient fabrication of robust superhydrophobic microarrays on metallic substrates remains a significant challenge. In this study, we designed a robust micro-pit array with excellent mechanical properties and developed an efficient method for creating the designed array on 304 stainless steel surfaces through the utilization of maskless electrochemical machining (ECM) technology. The resulting microarrays without the need for chemical modification exhibited excellent superhydrophobicity with a contact angle of 155.2° and a contact angle hysteresis of 2.5°, and this superhydrophobic performance possessed good stability. The microstructure and microhardness of the microarrays was subsequently investigated, and the results showed that the maskless ECM treatment significantly improved the mechanical robustness of the designed microarrays. In addition, the simulation and experiments indicated that the morphology and wettability of the fabricated surface could be well controlled by adjusting voltage parameters. The approach outlined in this work is efficient and scalable, and will promote the industrial production and practical application of superhydrophobic metallic surfaces with robust microarrays.

Effect of Pulse Conditions on Machining Characteristics in Bipolar-Pulse Electrochemical Machining of Cemented Carbide

Electrochemical machining was performed on two cemented carbides with different compositions using unipolar and bipolar short-pulse voltages to investigate the effects of the composition and pulse conditions on the machining characteristics. In the case of cemented carbides with high cobalt and low tungsten carbide (WC) contents, machining progressed even when a unipolar voltage was used. This is believed to be due to the dissolution of the binder, that is, Co, which causes the WC and WO3 particles to drop out. Machining progressed more easily when a bipolar voltage was used than when a unipolar voltage was used. This is attributed to the effective removal of WO3. The unevenness of the machined surface was also reduced with bipolar voltage. The negative pulse duration had to be sufficiently but appropriately long, because too long a duration increased the wear of the tool electrode. Even when bipolar pulse voltages were used, similar to the machining of general materials, a shorter positive pulse duration resulted in more precise machining. However, in the case of cemented carbide with low Co and high WC contents, the removal did not progress when a unipolar pulse voltage was applied. On the other hand, the machining progressed when a bipolar voltage was applied. However, if the positive pulse duration was excessively long, the amount of removal decreased. This is believed to be because the longer positive pulse duration increased the amount of WO3 generated, thereby inhibiting the current flow. Therefore, it is necessary to set an appropriate positive pulse duration to avoid the excessive production of WO3.

Implementation of robotic electrochemical machining in freeform surface machining with material removal rate prediction using different machine learning algorithms

Robots are used as machine tools via some advanced properties such as versatility, adaptation and mobility with other control systems. These advantages can be the solution to overcome the encountered problems in electrochemical machining (ECM). In this manner, the usability of a new machining method that is Robotic electrochemical machining (RECM) in freeform surface machining is investigated. Firstly, ECM parameters and their effects on the material removal rate (MRR) is discussed and compared with the literature. Experimental results showed that MRR variation for RECM acts similar characteristics with conventional ECM processes. The increase in voltage, electrolyte conductivity and feed rate increase MRR. The highest effect on MRR for both materials is voltage, electrolyte conductivity, and feed rate, respectively. Secondly, three different machine learning models are designed as Gaussian Process Regression (GPR), regression tree and deep neural network (DNN) models and the relationships between their actual and predicted values are discussed. The performance of the DNN model is better than other models with a correlation of determination values equal for Inconel 718 and AISI 1040. Furthermore, the DNN model with four input parameters outperforms developed models such as GPR and DTR with optimized hyperparameters regarding the R2, MSE, RMSE, and MAE. The change in height in the Z-axis and the surface roughness of the machined surfaces are also measured. The results show that the decrease in the Z axis is homogeneous, that is, uniform machining occurs and also the surface roughness has improved. Therefore, RECM can be a solution to machine free-form surfaces for different materials with high predictability.

Tooling aspects of micro electrochemical machining (ECM) technology: Design, functionality, and fabrication routes

Tooling aspects of micro electrochemical machining (ECM) technology: Design, functionality, and fabrication routes

Electrochemical dissolution behavior and electrochemical jet machining characteristics of titanium alloy in high concentration salt solution

Electrochemical dissolution behavior and electrochemical jet machining characteristics of titanium alloy in high concentration salt solution

Wire electrochemical contour evolution machining of gear involute artifact with horizontal electrode

Wire electrochemical contour evolution machining of gear involute artifact with horizontal electrode

Flow field optimization of pulse dynamic electrochemical machining for serpentine channels on stainless steel plates

Flow field optimization of pulse dynamic electrochemical machining for serpentine channels on stainless steel plates

Effect of inter-electrode gap on surface characteristics in conventional electrochemical machining

Conventional electrochemical machining (CECM) is an established toolroom process for the machining of conductive workpiece (W/P) substrates. In CECM, the material removal takes place through an electrochemical reaction between the cathode and anode. Significant studies have reported process parametric optimization of CECM with input parameters like voltage, feed rate, type of electrolyte and electrolyte concentration, etc., and their effect on the material removal rate (MRR), and surface roughness (Ra). But hitherto little has been reported on the effect of inter-electrode gap (IEG) and other CECM parameters in combination with a different tool and work materials. This study outlines the experimental investigations on CECM with a different tool and work materials based on Taguchi L18 orthogonal array (OA) on surface characteristics of machined surface for tool room applications in line with sustainable development goal (SDG) (with a special target on the industry, innovation, and infrastructure). The results suggest that for Ra, IEG is the most significant factor at a 95% confidence level. The results have been supported by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Ra analysis (with amplitude distribution function (ADF), and peak count (PC).

Effects of Circular Hydraulic Jump on the Material Removal Characteristics of Jet Electrochemical Machining

Jet electrochemical machining (Jet-ECM) is a potential precision machining method. Due to the advantages of non-stress-free machining and high flexibility, it is widely used in surface finishing and complex structural machining. However, the “w” shaped removal profile and wide removal range caused by inappropriate process parameters reduce the stability and localizability of Jet-ECM. In this paper, the material removal characteristics of Jet-ECM were investigated both theoretically and experimentally. A multi-physics field simulation model for Jet-ECM was established, and the overall shape of the circular hydraulic jump (CHJ), current density distribution and workpiece deformation were calculated. The effects of CHJ on the material removal characteristics were investigated by experiments with jet flow rate and inter-electrode gap (IEG) distance. The results reveal the qualitative relationship between CHJ states and process parameters and give the range of parameters that can form a stable CHJ and ensure a Gaussian shaped removal profile and a narrower removal range. This study provides theoretical guidance on the process parameters of Jet-ECM to improve its processing stability and localizability, which is significant for the accuracy of surface finishing and the controllability of complex structural machining, promoting the further application of Jet-ECM.

Enhancing Surface Integrity of Micro-Holes Machined on Inconel 718 using Shaped Tube Electrochemical Machining via Hydroxide Mixing

This research explores enhancing surface integrity of high aspect ratio (AR>5) micro-holes machined on Inconel 718 using Shaped Tube Electrochemical Machining (STEM) by mixing limited amount of metal hydroxides in the different electrolyte solutions. Typically, STEM employs hazardous acid solutions. These solutions cause machine corrosion, environmental risks, and harm to operators. This research aims to explore eco-friendly and safe alternatives. The efficacy of adding NaOH or KOH to eco-friendly neutral aqueous solutions of NaCl, KBr, and NaNO3 on machined surfaces is expounded. We assess electrolyte mixing parameters, including concentration and composition, and explore the effects of varying electrolyte temperature, voltage, and tool feed rate. Surface assessment uses SEM, EDX, XRD, and profilometry. Results reveal that adding hydroxides to neutral salt solutions improves surface roughness and reduces pitting. Hydroxide ions aid in dissolving oxide films during STEM of Inconel 718. Under specific conditions (9 g l−1, 18°C, 8 V, 0.8 mm min−1), NO3│OH yielded the lowest Ra (1.64 μm), while Br│OH resulted in the highest Ra (2.14 μm) with pitting, cracks, and deposits. NO3│OH exhibited a 25% decrease in Ra when a hydroxide concentration rise from 3 g l−1 to 15 g l−1. This research supports eco-friendly STEM for improved surface quality without process performance compromise.

Multi-objective parametric optimization of electrochemical machining of Inconel-625 superalloy

The high hardness value of Inconel-625 super alloy makes it difficult to machine with traditional machining methods. In this study, the machining of Inconel-625 has been attempted with electrochemical machining. The influence of input process parameters—voltage, feed rate, and flow rate of electrolyte has been studied on the output responses—material removal rate (MRR) and average surface roughness (SR). The experiments were performed following the central composite rotatable design of the response surface methodology. Analysis of variance has been used to test the significance of the process parameters and the model. A comprehensive empirical model representing the relationship between the process parameters and the response parameters has been developed. Further, the desirability function approach was used to acquire the optimal set of parameters. The optimal values of MRR and SR obtained in the study are 0.192837 gm./min and 0.99 μm, respectively, corresponding to the optimum settings of voltage, feed rate of the tool, and flow rate of electrolyte at 13.7 V, 0.20 mm/min, and 2.8 lit/min, respectively. The optimum settings so attained have been substantiated using confirmation experiments. The Confirmation tests show that the error between predicted and experimental values of MRR and SR was 2.02% and 4.8%, respectively, which fall in the acceptable range. Moreover, the surface characteristics of the machined area have been investigated using field emission scanning electron microscopy and 3D optical profilometer to analyze the machined surface's microstructure and 3D surface characteristics.