Jet Electrochemical Machining Research Articles

Fabricating Precise and Smooth Microgroove Structures on Zr-Based Metallic Glass Using Jet-ECM.

Zr-based metallic glasses (MGs) are promising materials for mold manufacturing due to their unique mechanical and chemical properties. However, the high hardness of metallic glasses and their tendency to crystallize at high temperatures make it challenging to fabricate precise and smooth microscale structures on metallic glasses. This limitation hampers the development of metallic glasses as molds. Jet electrochemical machining (jet-ECM) is a non-contact subtractive manufacturing technology that utilizes a high-speed electrolyte to partially remove material from workpieces, making it highly suitable for processing difficult-to-machine materials. Nevertheless, few studies have explored microgroove structures on Zr-based MGs using sodium nitrate electrolytes by jet-ECM. Therefore, this paper advocates the utilization of the jet-ECM technique to fabricate precise and smooth microgroove structures using a sodium nitrate electrolyte. The electrochemical characteristics were studied in sodium nitrate solution. Then, the effects of the applied voltages and nozzle travel rates on machining performance were investigated. Finally, micro-helical and micro-S structures with high geometric dimensional consistency and low surface roughness were successfully fabricated, with widths and depths measuring 433.7 ± 2.4 µm and 101.4 ± 1.6 µm, respectively. Their surface roughness was determined to be 0.118 ± 0.002 µm. Compared to non-aqueous-based methods for jet-ECM of Zr-based MGs, the depth of the microgrooves was increased from 20 μm to 101 μm. Furthermore, the processed microstructures had no uneven edges in the peripheral areas and no visible flow marks on the bottom.

Boundary fluid constraints during electrochemical jet machining of large size emerging titanium alloy aerospace parts in gas–liquid flows: Experimental and numerical simulation

Large size titanium alloy parts are widely used in aerospace. However, they are difficult to manufacture using mechanical cutting technology because of severe tool wear. Electrochemical jet machining is a promising technology to achieve high efficiency, because it has high machining flexibility and no machining tool wear. However, reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce, because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining. In addition, titanium alloy is very sensitive to fluctuation of the flow field, and a turbulent flow field would lead to serious stray corrosion. This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts. Based on the flow analysis and experiments, the machining flow field was effectively constrained. TB6 titanium alloy part with a perimeter of one meter was machined. The machined surface was smooth with no obvious machining defects. The machining process was particularly stable with no obvious spark discharge. The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.

The Development of the Stress-Free Polishing System Based on the Positioning Error Analysis for the Deterministic Polishing of Jet Electrochemical Machining.

Deterministic polishing based on jet electrochemical machining (Jet-ECM) is a stress-free machining method for low-rigidity and ultra-precision workpieces. The nozzle is equivalent to a special tool in deterministic polishing, and the workpiece material is removed using the mechanism of electrochemical dissolution at the position where the nozzle passes. By precisely regulating the nozzle's movement speed and dwell time, the quantity of material removed from the workpiece at a designated position can be finely adjusted. With this mechanism, the improvement of the workpiece shape accuracy can be achieved by planning the nozzle trajectory and nozzle movement speed. However, due to the positioning errors of the polishing device, the actual position of the nozzle may deviate from the theoretical position, resulting in errors in material removal amount, which affects the accuracy and stability of the polishing process. This study established a mathematical model to analyze the influence of nozzle positioning errors in deterministic polishing based on Jet-ECM. This model has been used to design a specific deterministic polishing device based on Jet-ECM. With the proposed deterministic polishing device, the surface shape of the workpiece is converged. The surface peak-to-valley (PV) value of the φ 50 mm workpiece (valid dimensions = 90% of the central region) indicated that the shape error of the surface was reduced from 2.67 μm to 1.24 μm in 34 min. The power spectral density (PSD) method was used to evaluate the height distribution and height characteristics of the workpiece surface. The results show that the low frequency spatial error is reduced significantly after processing. This study improves the accuracy of the stress-free deterministic polishing methods and further expands the use of deterministic polishing in industry.

A novel approach for predicting the complex geometry generated by electrochemical jet machining

A novel approach for predicting the complex geometry generated by electrochemical jet machining

Effect of Process Parameters on Joint Performance in Hot Pressure Welding of 6061 Aluminum Alloy to CF/PA66.

Polymer-metal hybrid structures combine the merits of polymer and metal materials, making them widely applicable in fields such as aerospace and automotive industries. However, the main challenge lies in achieving efficient and strong connections between the metal and polymer components. This paper uses the jet electrochemical machining (Jet-ECM) method to customize the surface morphologies on 6061 aluminum alloy (AA6061) sheets. The connection between AA6061 and carbon fiber-reinforced PA66 (CF/PA66) is then achieved through hot pressure welding (HPW). The effects of aluminum alloy surface morphology, welding force, and welding time on the mechanical properties and microstructure of the joint are investigated. The optimal process parameters are determined by the design of the experiment. The results show that the aluminum alloy surface morphology has the greatest impact on the mechanical property of the welded joint. The optimal process parameters are surface morphology with wider, shallower, and sparsely distributed grooves on the aluminum alloy surface, the welding force is 720 N, the welding time is 12 s, the welding temperature is 360 °C, the cooling time is 16 s, and the optimal peak load of the joint is 6690 N. Under the optimal parameters, the fracture morphology in the AA6061 side is almost entirely covered with CF/PA66. The joint experiences cohesive failure in most areas and fiber-matrix debonding in a small area.

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.

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

Modeling of Jet Electrochemical Machining Using Numerical and Design of Experiments Methods

Modeling of Jet Electrochemical Machining Using Numerical and Design of Experiments Methods

Investigation on tribo-characteristics of electrochemical jet machined part manufactured by laser powder bed fusion

Electrochemical jet machining (ECJM) is a toolless electrochemical-based material removal process suitable for finishing the Laser powder bed fusion (L-PBF) manufactured parts. However, the investigation of the tribological characteristics of the finished part is unknown. Therefore, in this article, an investigation was made to evaluate the tribological characteristics of the electrochemical jet machined surface of SS316L part produced by L-PBF. The experimental results revealed improvement in the roughness parameters after the ECJM. The wear tests revealed that the friction coefficients (COF) of the finished samples were significantly lower in comparison to the as-manufactured samples. During the investigation, the dominating mechanisms of the wear were found to be adhesive and delamination wear.

Gap effect in electrochemical jet machining

Electrochemical jet machining (EJM) is a young-generation micromachining and surface texturing technique with multiple merits. The materials removal function in EJM has traditionally been considered to be Gaussian-like and unaffected by changes in inter-electrode gap when maintaining a constant machining current. Nonetheless, phenomena that contradict this widely accepted perception are sometimes observed. In this paper, to clarify the inter-electrode gap effect in EJM, its impacts on flow field, electric field, and machined shape were studied by both experiments and simulation. With varied gaps ≥0.4 of nozzle diameter the jet profile keeps almost same and only its length changes, while narrowing the gap from 0.4 to 0.2 of nozzle diameter causes thinning of the jet-surrounding-film. Jet profile required for EJM cannot form with an overly tiny gap. In addition, the gap ≥0.6 of nozzle diameter features sufficiently long cylindrical jet portion that uniformly distributes the pass-through current density and eliminates the cathode-shape-determined electric field near nozzle to act on workpiece, resulting in constant materials removal function even though gap changes. With smaller gap the cathode-shape-determined electric field affects the anodic current density distribution and the materials removal function can be modulated by adjusting the gap, allowing EJM to generate geometry other than Gaussian-like profile. Furthermore, the influence of inter-electrode gap when using the specially-shaped nozzle was also investigated. With a small gap this method performs its ability in modulation of materials removal distribution by designing nozzle shapes, while a large gap such as ≥ nozzle diameter enables it to operate as a conventional nozzle.

Investigation of the microhole arrays generated by masked jet electrochemical machining with polyaluminum chloride electrolyte

Zirconium (Zr) alloy is a passivating metal with excellent general properties. The oxide films present on passivating metals make them resistant to corrosion by strong acid and alkali solutions, high-temperature water, and liquid metals. However, microfabrication of Zr alloy metal structures using existing machining methods suffers from low machining efficiency and poor machining quality. Electrochemical machining has advantages for processing Zr alloy metal microstructures. This study sought to evaluate the feasibility of masked jet electrochemical machining with a new electrolyte, polyaluminum chloride (PAC) of a microhole array in a Zr702 sheet. The dissolution behavior of Zr702 was analyzed with different concentrations of NaNO3, NaCl, and PAC. The electrochemical corrosion mechanism of Zr702 by using PAC was elucidated. A 2D model was established to analyze the evolution process of the sectional profiles of the microholes. Then, the effects of the main processing parameters were studied, and multifactor interaction response surfaces were analyzed. After optimizing the parameters, a high-quality microhole array was obtained with an average hole diameter of 152.11 μm, an average depth of 76.13 μm, a depth/diameter ratio of 0.501, a lateral corrosion coefficient of 2.023, a diameter variation coefficient of 1.71, and a depth variation coefficient of 2.87.

Cathodic discharge plasma in electrochemical jet machining: Phenomena, mechanism and characteristics

An ultrahigh voltage is frequently required in electrochemical jet machining (EJM) to produce extreme current densities (>900 A/cm2 for this study) to achieve maximum dissolution rates. However, such a high electric field easily induces a cathodic discharge at the nozzle, and the generation mechanism and characteristics remain unexplored. For the first time, this study shows a direct visualisation of the hydrogen evolution and cathodic discharge in EJM using high-speed photography. An in-depth analysis of the discharge behaviour was carried out based on electrical monitoring, temperature measurement, and characterisation of the resulting changes in the electrode surface. It was revealed that the current density threshold determines the discharge ignition. Discharge occurs preferentially at the inner edge of the nozzle end face, which can cause nozzle wear and reduce localisation of anode workpiece dissolution. The discharge intensity can be controlled by varying the applied voltage and pulse frequency. The electrolyte flow velocity and gap distance influence the discharge behaviour. With appropriate process control, cathodic plasma can enhance the EJM performance while minimising its negative impact. Furthermore, cathodic discharge can be significantly suppressed by designing the geometry of the nozzle tip to avoid local electric field concentration.

Control principle of anodic discharge for enhanced performance in jet-electrochemical discharge machining of semiconductor 4H-SiC

Implementing anode discharge into electrochemical jet machining (EJM) makes it possible to process semiconductor material 4H-SiC. However, the characteristics and control principle of anodic discharge behavior in EJM remains unclear, while it significantly influences material removal and EJM precision. The present study reveals discharge behavior and its impact on material removal by controlling the imposed electrical and chemical conditions. The physicochemical properties and spatiotemporal distribution of discharges are discussed by analyzing the plasma region's temperature, luminescence, and material removal fashion. The findings reveal that discharges are preferentially ignited in certain areas where the current density is concentrated. The discharge intensity and location are controllable by the pulse cycle and electrical field distribution inside the jet (i.e., changing the jet angle). Reducing pulse duration leads to more localized and mild discharges, improving machining precision. A gas ionization-dominated anodic discharge model is proposed. Both discharge and electrolyte types exert significant influence on material removal. Using a DC supply provides a maximum machining rate of 1.44 mm/min. Meanwhile, an optimal surface finish Ra 170 nm and high shape precision with no overcut is achievable by applying high-frequency AC of 1000 Hz.

Surface finishing of an additively manufactured part using electrochemical jet machining

The development and expansion activities of additive manufacturing (AM) are at their peak as complex parts with intricate features can be easily manufactured by various AM processes. However, obtaining a good surface finish for the AM parts has remained a challenging task. The surface defects and irregularities over intricate parts pose challenges during machining with conventional processes. Therefore, a simple, cost-effective, non-contact surface finishing approach is required to post-process the external and internal surfaces of AM metallic parts. This article reports the surface finishing of the SS316L part made by laser powder bed fusion (L-PBF) using a toolless electrochemical jet machining (ECJM), and investigations were performed to evaluate the different aspects of surface integrity. The experimental results revealed that surface irregularities and defects highlighted on the as-deposited samples were eliminated after ECJM.Moreover, after post-processing, the overlaid layer of oxides and carbides over the as-deposited sample surfaces was also removed. The maximum peak and valley height of the as-deposited surface were 30.1 µm and 41.6 µm, respectively. These heights have been reduced to 13.3 µm and 9.9 µm, respectively, while the arithmetical average roughness value 'Ra' has been reduced from 7.8 µm to 3 µm. The improvement in the mean value of 'Rz' and 'Ra' after post-processing was found to be 72%, and 61%, respectively. Therefore, the study concluded that the unique characteristic of the toolless electrochemical machining process is suitable for finishing the AM part.

Adapting ‘tool’ size using flow focusing: A new technique for electrochemical jet machining

Electrochemical jet manufacturing methods exploit the localised interaction of an electrified jet with a conductive workpiece. This has been exploited by numerous researchers to deposit and remove material. In recent studies, the same approach has been used as an analysis tool to measure and evaluate engineering components. The capability of this manufacturing method is limited by the resolution, which is governed by the diameter of the jet. Although approaches have been taken to reduce the kerf or interaction volume in the process, it is the jet diameter still provides the fundamental limit. In this study, a new method is proposed which takes advantage of a constriction effect to reduce the jet diameter through flow focusing, which occurs in coaxial two-phase flows. A novel nozzle arrangement is presented which demonstrates jets can be constricted by 79% leading to 54% reduction in machined kerf width. The limitations of this method are investigated in the context of fluid dynamic constraints, identifying optimum operating regions to utilise the approach in a computer numerical control machine tool arrangement. This enables continuously varying tool size in-process, which is analogous to other energy beam processes where spot size can be adjusted with a corresponding response influence.

Fabrication of oxide-free dimple structure on germanium via electrochemical jet machining enhanced by opposing laser irradiation

The electrochemical machining (ECM) of germanium (Ge) wafer can be significantly improved in terms of efficiency and localization by introducing laser irradiation. However, residual oxide particles usually exist when using neutral electrolyte. In this study, the NaNO3 electrolyte jet is formed via a cathodic nozzle and impacts perpendicularly on the bottom of the Ge wafer, at which position the nanosecond (ns) laser irradiates from opposing side to locally and precisely enhance the electrical conductivity. In this way, the dimple structure without any detectable oxidation products can be efficiently fabricated. Characterization of surface morphology is then amply conducted. The radial lines consisting of regular micro-waving structure are usually noticeable, especially near the dimple edge, which may be attributed to the rapid and radial electrolyte flow along the concave sidewall. In contrast, irregular corrugated pattern can be observed near the dimple center, which may be caused by the electrolyte turbulence after impingement. In addition, parametric experimental study has been carried out, and the effects of the applied voltage, laser power and electrolyte concentration on the dimple profile and surface characteristics have been respectively detailed discussed. Finally, simulation study of the electrolyte flow field is conducted to reveal the distribution regularities of velocity and pressure, to deepen the understanding of formation mechanism of the complex surface morphology.

Experimental study on the evolution process of Zr702 microdimple array generated with masked jet electrochemical machining

Experimental study on the evolution process of Zr702 microdimple array generated with masked jet electrochemical machining

Material Removal Mechanism in Photocatalytic-Assisted Jet Electrochemical Machining of SiCp/Al.

Silicon carbide particle reinforced aluminum matrix (SiCp/Al) composites are increasingly used in high−end industries because of their superior comprehensive material properties. However, their advanced properties also create severe challenges for traditional processing technologies. A new hybrid machining method named photocatalytic−assisted jet electrochemical machining (PAJECM) is proposed to improve the machining capability by synchronously removing the metal aluminum matrix and the SiC particles. Comparative experiments were carried out on whether photocatalysis was added. The results show that after photocatalytic−assisted jet electrochemical machining, the height of SiC particles’ extrusion on the surface is significantly reduced. Compared with jet electrochemical machining (JECM) without photocatalysis at the same processing voltage, the surface roughness value is reduced, and the processing quality is improved. In PAJECM, the aluminum matrix is removed by electrochemical anodic dissolution, while the SiC particles generate a SiO2 reaction layer through photocatalysis, and the TiO2 abrasive flow’s mechanical action repeatedly removes the reaction layer. The electrochemical polarization curves and energy diffraction spectroscopy elemental analysis confirmed the material removal mechanism of PAJECM. Based on analyzing the phenomenon of material removal in detail, a qualitative model of the PAJECM material removal mechanism is established. This study provides valuable insights into the material removal mechanism in photocatalytic and jet electrochemical machining composite processes.

Plasma-enabled electrochemical jet micromachining of chemically inert and passivating material

Electrochemical jet machining (EJM) encounters significant challenges in the microstructuring of chemically inert and passivating materials because an oxide layer is easily formed on the material surface, preventing the progress of electrochemical dissolution. This research demonstrates for the first time a jet-electrolytic plasma micromachining (Jet-EPM) method to overcome this problem. Specifically, an electrolytic plasma is intentionally induced at the jet-material contact area by applying a potential high enough to surmount the surface boundary layer (such as a passive film or gas bubble) and enable material removal. Compared to traditional EJM, introducing plasma in the electrochemical jet system leads to considerable differences in machining performance due to the inclusion of plasma reactions. In this work, the implementation of Jet-EPM for fabricating microstructures in the semiconductor material 4H-SiC is demonstrated, and the machining principle and characteristics of Jet-EPM, including critical parameters and process windows, are comprehensively investigated. Theoretical modeling and experiments have elucidated the mechanisms of plasma ignition/evolution and the corresponding material removal, showing the strong potential of Jet-EPM for micromachining chemically resistant materials. The present study considerably augments the range of materials available for processing by the electrochemical jet technique.

Significance of waveform design to achieve bipolar electrochemical jet machining of passivating material via regulation of electrode reaction kinetics

Electrochemical machining (ECM) using the bipolar pulse technique shows significant potential for the effective machining of prone-to-passivation materials. However, despite its success in machining specific materials (e.g. tungsten carbide), the underlying mechanism remains unclear. This study presents an in-depth analysis of the interplay between cathodic polarisation (CP) and anodic oxidation in bipolar pulse electrochemical jet machining (bipolar-EJM). An observational study of the structural changes in the anodic oxide film indicated that the oxide broke down by electrochemical reduction and mechanical damage when subjected to CP. The electrochemical kinetics at the electrode interface, particularly the proton transport and discharge reactions, were discussed to elucidate the mechanism. This study first discloses that the bipolar pulse waveform plays a crucial role in overcoming the oxide film and achieving machining in bipolar-EJM. Variations in waveform shape result in distinct interactions of the cathodic pulse with the anodically formed surface oxide. A principal approach of bipolar-EJM was thus developed to effectively remove or eliminate passive oxide films by controlling the bipolar pulse. The material removal mechanism of the developed method is described and the corresponding kinetic model of the electrode reactions is presented. For verification, the bipolar-EJM of the strongly passivating metal niobium (Nb) is first demonstrated in a pH-neutral NaNO3 aqueous solution, demonstrating the effectiveness of the proposed method. The new insights into the bipolar pulse process established here will is believed to provide valuable guidance to advance the bipolar electrochemical process, including ECM and electrochemical polishing.