Electrochemical Machining Research Articles

Reproduction of Three-Dimensional Microstructures on Inconel 718 Utilizing Laser-Textured PECM Cathodes

Abstract Pulse electrochemical machining (PECM) is an unconventional material removal process, widely applied to machine or shape difficult-to-machine materials. A new concept of reproducing three-dimensional (3D) microstructures has been developed and elaborated. Picosecond laser was utilized to produce concave or convex patterns on PECM cathodes, and pattern replication was carried out to PECM anodes. The laser achieved high machining precision and excellent surface integrity; both patterns were successfully replicated on the anodes. However, considerable deviations were found in the reproduced concave patterns on the anodes, possibly due to the rounding and widening effects.

Investigation of the influence of electrolytic milling machining parameters on the machining accuracy of thin-walled parts.

Aircraft parts are often designed as thin-walled structures to reduce the weight of the aircraft. However, thin-walled structures are prone to deformation during the milling process, leading to a decrease in machining accuracy. To address this problem, a method combining milling and electrochemical machining, known as electrolytic milling, is proposed to minimize deformation and enhance the accuracy of thin-walled parts. The factors that affect the machining accuracy of electrolytic milling were analysed, and a model for predicting the thickness of the material removed was established. Electrolytic milling experiments were designed, and the model was solved. Based on the built model, the influences of feed rate, spindle speed, radial cutting depth, voltage and electrolyte concentration on material removal thickness were investigated. Compared with the milling method, the electrolytic milling method can improve the machining accuracy of thin-walled parts. Electrolytic milling experiments were conducted on box-shaped parts to verify the reliability of the proposed method.

Investigation of dissolution behavior and surface integrity in electrochemical machining of nickel-based superalloys

ABSTRACT Dissolution behavior and surface integrity during the electrochemical machining (ECM) of nickel-based superalloys are vital for the performance of components. This study examines IN718, 718Plus, and Rene 65 alloys focusing on material removal mechanisms, surface morphology, intergranular corrosion, three-dimensional profiles, surface roughness, microhardness, and residual stresses. The results indicated that as the current density increased, the MRR of all three alloys increased linearly, while the current efficiency initially fluctuated before stabilizing. At low current densities, selective dissolution and intergranular corrosion resulted in rough surfaces for the alloys examined. In contrast, higher current densities produced smooth and uniform surfaces for these alloys. After electrochemical treatment, the surface microhardness of all alloys was reduced, and there was a slight decrease in residual stresses as well. These findings support the development of more precise and effective strategies for achieving higher surface integrity in the ECM of nickel-based superalloys.

Investigation of Electrochemical Discharge Machining for Tungsten Carbide: Effects of Electrolyte Composition on Material Removal Rate and Surface Quality

Abstract Tungsten carbide (WC-Co) with a cobalt binder has been widely used in industrial application. Through their high wear resistance and hardness, which make it a challenge to machine. Electrochemical discharge machining (ECDM) is a newly developed hybrid technique used to machine conductive and nonconductive materials. Tungsten carbide machining is an area that needs more investigation. In this study, different types of electrolytes have been tested in the electrochemical machining of tungsten carbide. It has been concluded that tungsten carbide was successfully machined with electrolytes that were either neutral salts or a combination of neutral salts and hydroxides, the highest material removal rate achieved was (0.09250 g/min), and the average surface roughness achieved in this work was measured at (Ra 0.9275 µm). However, deposition took place on the surface of machined tungsten carbide when the samples were treated with sodium hydroxide and potassium hydroxide. EDX analysis of successfully machined tungsten carbide samples reveal the presence of carbon (C) due to diffusion from the base material and oxygen (O), most likely due to oxidation brought on by the high temperatures utilized. Scanning electron microscopy confirmed that the machined surfaces had craters, pores, restricted microcracks, and re-deposited melt particles, among other things.

Electrochemical cutting with flexible electrode of controlled online deformation

Abstract Improvements in aero-engine performance have made the structures of the aero-engine components increasingly complex. To better adapt to the processing requirements of narrow twisted channels such as an integral shrouded blisk, this study proposes an innovative method of electrochemical cutting in which a flexible tube electrode is controlled by online deformation during processing. In this study, the processing principle of electrochemical cutting with a flexible electrode for controlled online deformation (FECC) was revealed for the first time. The online deformation process of flexible electrodes and the machining process of profiles were analysed in depth, and the corresponding theoretical models were established. Conventional electrochemical machining (ECM) is a multi-physical field-coupled process involving electric and flow fields. In FECC, classical mechanics are introduced into the tool cathode, which must be loaded at all times during the machining process. Therefore, in this study, before and after the deformation of the flexible electrode, a corresponding simulation study was conducted to understand the influence of the online deformation of the flexible electrode on the flow and electric fields. The feasibility of flexible electrodes for online deformation and the validity of the theoretical model were verified by deformation measurements and in situ observation experiments. Finally, the method was successfully applied to the machining of nickel-based high-temperature alloys, and different specifications of flexible electrodes were used to complete the machining of the corresponding complex profiles, thereby verifying the feasibility and versatility of the method. The method proposed in this study breaks the tradition of using a non-deformable cathode for ECM and adopts a flexible electrode that can be deformed during the machining process as the tool cathode, which improves machining flexibility and provides a valuable reference to promote the ECM of complex profiles.

Anodic Dissolution Behavior of DD6 Nickel-Based Single Crystal Superalloy for Electrochemical Machining Applications

Abstract Nickel-based single crystal superalloys have been widely used in turbomachinery components. Electrochemical machining (ECM) is an essential method for shaping such high-performance alloys. Understanding the fundamentals of ECM for these alloys is crucial for the design and optimization of the process. This study investigated the anodic dissolution of DD6 nickel-based single crystal superalloy in concentrated NaCl and NaNO3 electrolytes under ECM conditions. Polarization curves showed a passive-transpassive transition behavior in both electrolytes. Galvanostatic experiments demonstrated unique current efficiency characteristics contradicting the empirical ECM knowledge. Surface analyses revealed that the anomalous current efficiency of >100% in the NaNO3 electrolyte results from the falling of γ’ phases from anodic surfaces due to the preferential dissolution of the γ matrix phase. The transition from selective to uniform dissolution with increased current density and reduced electrolyte flow velocity leads to decreased current efficiency in NaNO3 electrolyte. The removal of both γ and γ’ phases depends entirely on electrochemical dissolution in NaCl electrolyte, ensuring that current efficiency maintains a normal value. A schematical anodic interface model was proposed to describe the dissolution behavior.

Fabrication of Die Sink Electrochemical Machining Tools Using Low Melting Fusible Alloy and Polymer Based Additive Manufacturing

The present work introduces a novel approach to fabricating die-sink tools for electrochemical machining (ECM) using low-melting fusible alloy and additive manufacturing. Three methods are proposed, each bettering the previous in manufacturing sustainability. The versatility of the process enables the fabrication of die-sink ECM tools that are hitherto considered challenging to fabricate. Finite element analysis was used to simulate the temperature rise of the low-melting (50 °C) tool due to Joule heating, accounting for electrolyte flow under various process parameters. A novel validation method employed a thermostat temperature probe as a cathode. Experiments based on the simulation data revealed that for a 4 mm tool diameter, the tool is unlikely to melt at 3 A current, 200 μm inter-electrode gap, 11.97 S m−1 electrolyte conductivity, and 1.7 m s−1 electrolyte velocity. A pulsed power supply was subsequently used to improve heat dissipation, and ECM was successfully carried out using tools of various shapes, demonstrating the effectiveness of the developed fabrication methods.

Electrochemical jet machining in deep-small holes with gas assistance: generating complex features on internal surfaces

Deep-small holes with internal features have important applications in thermal engineering but pose significant difficulties for traditional machining methods. Electrochemical jet machining (EJM) is an effective surface micromachining technique with numerous merits. Applying EJM to create complicated features on the internal surface of deep-small holes is attractive. However, this concept remains challenging due to the narrow and enclosed processing space. In this work, a novel gas assistance tool is developed to achieve the EJM process in deep-small holes for the first time. The hydrodynamic conditions to realize well-shaped and unsubmerged jets in both open space and deep-small holes using the specifically designed tool are investigated. The appropriate electrolyte flow rate and sidewall orifice dimensions enable the desired jet to be ejected laterally from the tubular cathode sidewall orifice. While in the deep-small hole the assist gas creates a local gas cavity around the orifice to prevent the jet from submerging, forming the jet shape required for EJM and consequently achieving localized machining of the internal surface. Excessive assist gas pressure should be avoided as it causes the jet to incline and deform, resulting in reduced machining accuracy. Furthermore, the influence of the main parameters on machining performance is examined. The developed gas-assisted EJM method demonstrates similar machining characteristics to the conventional EJM process when appropriate gas assistance conditions can produce the well-shaped unsubmerged jet. As such, various features with smooth surfaces and good shape accuracy are successfully machined on the internal surface of deep-small holes.

Optimizing the surface quality of electrochemical machined Ni-based single crystal superalloy via manipulation of phase and dendrite dissolution

The transpassive dissolution behaviors of Ni-based single crystal superalloy in 10 %NaCl, 10 %NaNO3, and mixed solution are investigated by using potentiodynamic polarization, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The alloy exhibits opposite yet complementary dissolution characteristics in NaCl and NaNO3 solutions. The different responses of γ/γ′ phases to Cl− and NO3− contribute to the opposite dissolution behaviors of dendrites and interdendritic regions. The surface flatness is noticeably enhanced in mixed solution due to the synchronous dissolution of the γ/γ′ phases. Our work paves the way for obtaining high-quality surface in electrochemical machining of single crystal superalloys.

Cross-scale electrochemical machining of superhydrophobic end face cavities via microstructured surface cathodes

In order to solve the problems of low precision of the electrochemical machining cavity and poor end face quality, this paper proposed a microstructured surface cathode and established the electrical and flow field models of the machining process. Theoretical analysis and simulation results show that the microstructure surface is helpful to improve the current density of the machining gap, and due to the superhydrophilic characteristics of the surface, hydrogen bubbles are promoted to separate from the cathode surface, the volume fraction of hydrogen bubbles in the end gap is reduced, and the mass transfer efficiency of the electrolyte is improved. A nanosecond laser machining system is used to prepare the array microstructure on the cathode surface. Compared with the experimental results of the original cathode, the feed rate of the proposed cathode increased from 0.10 mm/min to 0.20 mm/min and the machining process is more stable. The standard deviation of the width along the cavity depth direction is reduced from 285 μm to 175 μm, improving the machining accuracy of cavity. In addition, the microstructure on the cathode surface is replicated on the cavity end face and the reasons for the differences in size and shape between the micro-pit structure on the cavity end face and the microstructure on the cathode surface are analysed. The static contact angle of the cavity face is measured to be 150.5°, demonstrating excellent superhydrophobic properties. This method realizes cross-scale electrochemical machining of millimetre-scale cavities and micron-scale pits.

Photocatalytic-assisted electrochemical machining of SiCp/Al: An exploration of mechanisms and effects

Photocatalytic-assisted electrochemical machining of SiCp/Al: An exploration of mechanisms and effects

Electrochemical machining post-processing of additively manufactured nickel-based superalloys via laser directed energy deposition

ABSTRACT The electrochemical machining post-processing of additively manufactured nickel-based superalloys was studied to solve the contradiction between material processing efficiency and accuracy. The research results show that the surface of the fabricated specimens presented an uneven undulating morphology due to the overlapping of the cladding tracks and the stacking of the cladding layer in the process of laser directed energy deposition. After electrochemical machining post-processing, the levelling degree of the specimen surface gradually increased with the processing. However, at the same time, the levelling efficiency of the electrochemical machining post-processing gradually decreased due to the gradual decrease of the current density difference between the peaks and valleys on the specimen surface. The current efficiency remained basically unchanged at 67.6% throughout the electrochemical machining post-processing. This study provides experimental basis and theoretical foundation for the development of new combined machining technology of nickel-based superalloys based on laser directed energy deposition and electrochemical machining.

A simple method for insulating sidewalls of the cathode tool to enhance precision in ECDM

Conventional micro-turning of metal materials with low rigidity and hardness is highly challenging. Electrochemical Discharge Machining (ECDM) offers an alternative approach for fabricating micro shafts. However, micro-turning by ECDM often leads to severe flaring at the shaft shoulder due to stray corrosion. To mitigate this issue, we propose two novel methods for insulating the sidewalls of the cathode tool: applying insulating tape to the sides of a rectangular cathode tool or attaching aluminum foil along the bottom edge of a rectangular acrylic plate. We evaluated the machining performance of these cathode tools on the 3 mm diameter copper rods. Experimental results demonstrate that using an acrylic plate with attached aluminum foil as the cathode tool significantly enhances machining accuracy in the transition area of the shaft shoulder. Additionally, the simplicity and reliability of this method highlight its advantages.

Electrochemical Machining of Micro-Pit Arrays on a GH4169 Alloy with a Roll-Print Mask Using a C6H5Na3O7-Containing NaNO3 Mixed Electrolyte.

GH4169 alloy, a nickel-based superalloy known for its excellent high temperature resistance, corrosion resistance, mechanical properties, and high-temperature tribological properties, is widely used in industrial applications, such as in gas turbines for space shuttles and rocket engines. This study addresses the issue of electrolyte product residue in the electrochemical machining process of a GH4169 alloy by utilizing a C6H5Na3O7-containing NaNO3 new mixed electrolyte. Comparative investigations of the electrochemical behavior and electrolyte product removal mechanisms at different concentrations of C6H5Na3O7 additive in NaNO3 solutions were conducted. The effects of additives, applied voltage, and the rotating speed of the cathode tool on the processing performance of micro-pit arrays on a GH4169 alloy were analyzed. The results indicate that the mixed solution containing C6H5Na3O7 significantly improves the localization and geometric morphology of the micro-pits compared to a single NaNO3 solution. The optimal electrochemical machining parameters were identified as 0.5 wt% C6H5Na3O7 + 10 wt% NaNO3 mixed electrolyte, 12 V applied voltage, and 0.1 r/min rotating speed of the cathode tool. Under these conditions, high-quality micro-pit arrays with an average diameter of 405.85 μm, an average depth of 87.5 μm, and an etch factor (EF) of 1.67 were successfully fabricated, exhibiting excellent morphology, localization, and consistency.

Hard Particle Mask Electrochemical Machining of Micro-Textures

The efficient and cost-effective preparation of masks has always been a challenging issue in mask-based electrochemical machining. In this paper, an electrochemical machining process of micro-textures is proposed using hard particle masks such as titanium and zirconia particles. Numerical simulations were conducted to analyze the formation mechanisms of micro-protrusion structures with insulating and conductive hard particle masks, followed by experimental verification of the process. The results indicate that when the hard particles are electrically insulating, metal material preferentially dissolves at the center of the particle gap, and the dissolution then expands over time in depth and towards the particle contact points. Conversely, using the conductive particles as the masks, such as titanium particles, dissolution initially occurs in a ring region centered at the contact point between the hard particle and the anode, with a radius approximately one-quarter of the chosen particle’s diameter (200 μm), and then continues to expand outward.

Comparative Analysis of Simultaneous Electrochemical and Electrodischarge Machining Process

Abstract Recent advances have established electrochemical discharge machining (ECDM) as an effective alternative to electrical discharge machining (EDM) for producing microholes in conductive materials. However, ECDM leaves nonuniform layers, including recast layers and heat-affected zones, rendering it unsuitable for materials vital to aerospace, defence, and biomedical applications. To address this issue, the present work investigates a novel electrochemical machining (ECM)-based frugal engineering process known as simultaneous electrochemical and electrodischarge machining (SECEDM) for microhole fabrication. To evaluate the process effectiveness, the machining results of the SECEDM process were compared with ECDM, EDM, and ECM. The obtained results present the fundamental distinction between the process mechanism of SECEDM and ECDM. SECEDM has been reported to produce microholes with improved machined surfaces characterized by their freedom from recast layer and ECDM-induced defects. Moreover, SECEDM facilitated meticulously controlled high-speed anodic dissolution of work material, surpassing the material removal rate (MRR) achieved through ultrasonic-assisted ECDM (U-ECDM), ECM, and EDM processes by 2.67, 4.2, and 6.2 times, respectively. Furthermore, the substantial 67.72% and 68.82% reduction in the average machined hole diameter than ECM and U-ECDM, respectively, with a noteworthy 13.69% enhancement in average roundness error achieved while maintaining the repeatability accuracy with an accuracy range within ±0.009 mm through SECEDM process underscore SECEDM's accuracy and repeatability. In addition, lower surface roughness by 31.6% and 68% compared to ECM and EDM, along with reduced carbon and oxygen content as examined through energy dispersive X-ray (EDX) analysis, signifies the SECEDM process efficiency in microfabrication.

Pulse dynamic regulation of electrochemical discharge milling by utilizing the slotted tube electrode

Electrochemical discharge machining (ECDM) has a splendid application potential for machining difficult-to-cut materials. It is a challenge to limit and control the discharge energy and area of DC power supply in ECDM. Owing to the uncertainty and randomness of the position and range of the single discharge, the unpredictable discharges deteriorate the surface quality of the workpiece, alter the size of the inter-electrode gap (IEG), and influence the distribution of the multi-physical fields. Therefore, to regulate the machining state and energy, the ideology of pulse dynamic machining is introduced, and a method of pulse dynamic ECDM utilizing the slotted electrodes is proposed. With the tool electrode rotating, the tube electrode transforms the pure electrochemical machining (pure-ECM) stage and the electrochemical discharge machining (ECDM) stage periodically through the slots at the bottom of it. The machining current waveform, surface roughness and sidewall taper of machined grooves, material removal rate (MRR), and relative tool wear rate (RTWR) are investigated. Additionally, the discharge types of the ECDM are explicitly defined and statistically classified. The experimental results show that the pulse dynamic regulation of hybrid machining using the slotted electrodes is beneficial to regularize the machining current waveform and optimize the machining quality.

Performance analysis of wire-electrochemical discharge cutting of glass material

The present study investigated the feasibility of micro-cutting in glass material by using Electrochemical Discharge Machining (ECDM) Process. Glass possesses outstanding properties that make it a versatile with widely used in a diverse range of applications. Because of its tendency to fracture brittle during machining, glass is typically processed in its liquid or viscous state to manufacture precise and high-quality parts. Machining glass with good dimensional accuracy is a challenging task due to its fragile nature. Therefore, researchers have recognized the very appropriate technique for machining glasses with precision. The Wire-Electrochemical Discharge Machining (WECDM) has been identified as the most economical and efficient technique for fabricating micro slits in thin glass samples. In the present work, an in-house setup for WECDM was developed and the feasibility of the developed configuration was examined. Two different thicknesses of glass specimen have been considered for experimentation for checking the quality of cut and it is found that thinner specimen possesses good quality cut. The regression model has been developed to find a relationship between input and response parameters. The developed regression model was reasonably well fitted with the observed values where applied voltage 55V, 15% by wt. electrolyte concentration and 70% duty cycle were the most influencing parametric combinations among others. Further mixed electrolytes have shown excellent performance up to a certain concentration in terms of Material Removal Rate (MRR). This study reveals that optimal capillary action, influenced by surface tension and electrolyte concentration, is crucial for consistent sparking and efficient material removal in WECDM.

Electrochemical machining of complex structures on thin-walled plates using pure rolling cathode tool

Electrochemical machining of complex structures on thin-walled plates using pure rolling cathode tool

Enhanced error correction for adaptive electrochemical machining of eccentric bushings

Enhanced error correction for adaptive electrochemical machining of eccentric bushings