Electrochemical arc milling (ECAM) has emerged as a promising technique for machining complex structures in difficult-to-cut materials. However, the coupled effects of electrochemical dissolution and discharge erosion cause severe machining overcut and electrode wear, thus causing the inter-electrode gap (IEG) to evolve continuously. Consequently, conventional toolpath planning methods generate significant deviations between the programmed trajectory envelope of electrode and the actual machined boundary. To address this challenge, an experimentally calibrated dynamic equivalent electrode is introduced as a process-informed representation of the effective machining envelope. Its equivalent diameter and depth directly quantify the lateral and axial material removal boundaries within the groove. Based on this representation, an electrode-compensation-based hybrid constant-depth and constant-offset contour (EC-CDCOC) toolpath generation strategy is proposed. The framework integrates intra-layer compensation for feed-direction depth variation, inter-layer compensation for accumulated axial electrode wear, and equivalent-diameter compensation for lateral contour control. The required geometric and wear-related parameters are identified through groove machining experiments and incorporated into executable cavity toolpaths. During layer-by-layer machining, the evolution of the electrode transition region is further characterized, and an additional equivalent-diameter correction is introduced to account for the observed protrusion-related enlargement of the effective machining width. Comparative experiments demonstrate that, when optimized for axial compensation and offset distance, the proposed modified strategy increases the material removal rate (MRR) by 126.7% compared to the conventional contour-offset contour (COC) toolpath. Concurrently, the dimensional accuracies of cavity side length and depth are improved by 56.6% and 71.3%, respectively. The strategy is further validated by machining circular, triangular, pentagram-shaped, and thin-wall structures. The results demonstrate that the proposed framework provides a practical approach for integrating process-dependent removal characteristics and electrode wear into ECAM toolpath generation.

Electrolyte composition critically influences the electrochemical corrosion behavior of powder metallurgy superalloys, directly impacting machined surface quality. This study investigates ethylene glycol as a substitute for water, and reveals distinct differences in the electrochemical dissolution, in particular phase-specific dissolution behavior of Rene 104, when using aqueous versus ethylene glycol-based electrolytes. Polarization curves, open circuit potential, electrochemical impedance spectroscopy, and current efficiency tests are employed to elucidate passive film composition, valence state distribution, and formation mechanisms in different electrolytes. In addition, a point defect model is introduced to explain passivation film growth. Results show Rene 104 lacks a stable passivation region in aqueous solutions, leading to high ion mobility and defect formation rates. The primary gamma(y)p phase, having a higher potential, preferentially dissolves, resulting in a porous, honeycomb-like surface. In contrast, ethylene glycol's high viscosity and complexation ability reduce defect migration and dissolution rates, resulting in the formation of a denser, more stable passive film. This slower gamma(y)p phase dissolution yields a smoother surface. Moreover, in the NaCl ethylene glycol solution, surface roughness after dissolution remains unaffected by current density. A dedicated experiment further confirms that NaCl in ethylene glycol facilitates high surface quality machining of Rene 104. Ethylene glycol-based electrolytes offer a practical route to achieve high-quality, precision machining of powder metallurgy superalloys, such as Rene 104, with improved surface stability and process robustness.

SiC-particle-reinforced Al (SiCp/Al) metal matrix composites (MMCs) have attracted considerable attention in high-end manufacturing fields such as electronic packaging and aerospace. The surface condition after machining has a significant impact on their subsEq.uent service performance. The electrolyte solvent plays a critical yet underexplored role in governing passivation film evolution and electrochemical dissolution. Here, the solvent-dependent behavior of SiCp/Al composites is systematically investigated in NaCl-aqueous and NaClethylene glycol (EG) electrolytes with identical conductivity. Based on the point defect model, the influence of the solvent environment on passivation film growth, destruction, and associated dissolution behavior is elucidated. The results suggest that the EG solvent modifies interfacial reaction kinetics and point defect evolution, thereby enhancing film stability. In NaCl-aqueous electrolyte, the high activity of H2O and OH- promotes defect generation and transport, while Cl- ingress may lead to defect accumulation and localized film breakdown, resulting in non-uniform dissolution. In contrast, the reduced water activity in the NaCl-EG electrolyte suppresses defect generation, and the possible formation of an organic-enriched interfacial layer may inhibit Cl- penetration and promote film densification. As a result, charge transfer resistance increases, leading to slower and more uniform material dissolution. Although the NaCl-EG electrolyte exhibits relatively lower dissolution efficiency, improved surface integrity is achieved, including reduced roughness (2.016 mu m to 1.055 mu m), smaller wettability variation (29.211 degrees), and lower residual stress evolution (12.96 MPa). Comprehensive characterization indicates that the NaCl-EG electrolyte helps preserve relatively stable surface characteristics, demonstrating its potential for controlled electrochemical machining of SiCp/Al composites.

The electrochemical properties of surface oxide films significantly influence the localized dissolution behavior in jet electrochemical machining (JEM). In this study, 2219 aluminum alloy was selected as the model material. By adjusting the surface oxidation state to regulate the charge consumption required for material removal, the influence of oxide film breakdown characteristics on dissolution behavior and microstructure formation was investigated to improve the microstructure aspect ratio. Among the three typical films, the passivation film (similar to 493 nm) was loose and porous and exhibited poor electrochemical stability and the lowest breakdown charge threshold. The natural oxide film (similar to 19.4 nm) was compact and uniform with a moderate threshold. In contrast, the laser-modified film (similar to 649 nm) possessed a dense inner and porous outer layer, offering the highest breakdown charge threshold and superior corrosion resistance. Differences in breakdown charge due to surface state strongly affected dissolution behavior within the machining region, as indicated by simulations. Experimental results further demonstrated that laser-modified samples required the lowest current, significantly suppressed lateral dissolution, and produced the narrowest and shallowest grooves. Based on these findings, a local laser modification strategy was proposed, creating differentiated surface states in different regions of the same workpiece to control material dissolution and enhance microstructure aspect ratios selectively. This strategy offers a novel approach for fabricating high aspect ratio microstructures, enabling on-demand precision machining of distinct regions within complex structures. It may be extended to other materials prone to oxidation or passivation, such as titanium alloys.

Electrochemical Arc Machining (ECAM) has demonstrated considerable potential for efficient machining of difficult-to-cut materials. However, the relationships between machining signals and material removal characteristics in ECAM are poorly understood. In this study, the impedance characteristics of ECAM machining circuit were investigated. Results show that the equivalent impedance of arc discharge is significantly less than that of Electrochemical Machining (ECM), leading to a higher arc discharge current. As the feed rate increases, the Inter-Electrode Gap (IEG) decreases, resulting in higher arc discharge frequency, longer sustaining time, and increased peak current. Arc discharges in a small IEG exhibit a high electrical equivalent, which is 2.34 times that of ECM. At a feed rate of 200 mm/min, arc discharge contributed to 93.59% of the total material removal, achieving a Material Removal Rate (MRR) of 751.96 mm3/min. Furthermore, with increasing tool electrode feed rate, more electrical energy was effectively utilized for arc discharge processes. Under these conditions, a larger proportion of the arc discharge energy was allocated to the workpiece, minimizing the relative electrode wear rate to 4.61%. The enhanced arc discharge effect led to a significantly recast layer, while the electrochemical effect remained relatively stable. Consequently, the groove dimensional characteristics and surface morphology were predominantly influenced by arc discharge behavior. This study elucidates the intrinsic relationship between material removal mechanisms and machining current in ECAM, thereby offering a foundation for machining optimization and industrial application. Finally, the ECAM technique was successfully utilized for the efficient machining of an optical load-bearing structure.

Wire electrochemical machining (WECM) offers a promising solution for processing high-strength, high-hardness materials for aeroengine components. However, scattered corrosion and nonconcentrated electric fields hamper the process. In mitigation, pulse dynamic WECM (PD-WECM) has been proposed to optimize electric field distribution during cutting, significantly reducing slit width while achieving superior surface quality. This method involves categorizing the surface of the rotating electrode into active (work) and inactive (non-work) areas from a circumferential perspective. A chopping system is employed to synchronize power with work-area alignment, thereby concentrating the electric field and enhancing the mass transfer using wedged electrodes with insulating coatings. The chopping system reduces surface roughness to 0.59 mu m, a 43 % decrease, and the wedged electrodes minimize slit width by 401 mu m (17 %) compared to the result machined by circular electrode without the chopping system, thus enhancing mass transfer efficiency. Compared with continuous-electric-field WECM, our chopping technique is superior. Under conditions involving a 180 degrees power-on angle using wedged electrodes with insulating coatings, we stabilized the slit sidewall roughness at similar to 0.254 mu m and maintained a slit width of similar to 1.3 mm.

Inconel 939 (IN939) exhibits excellent high-temperature strength and oxidation resistance, enabling its widespread application in key hot-end components of gas turbines. Electrochemical machining (ECM) offers advantages for precision machining of superalloys, where electrolyte composition critically influences its electrochemical dissolution behavior and surface quality. This study investigates the dissolution behavior and ECM response characteristics of IN939 in NaCl and NaNO3 electrolytes. Electrochemical results reveal that the NaNO3 electrolyte forms a Cr2O3-dominated interfacial film with high impedance, indicating stronger interfacial stabilization. In contrast, the NaCl electrolyte produces a relatively porous interfacial film enriched in Al2O3, which is more conducive to maintaining an active dissolution state. This difference originates from the electrolyte-dependent dissolution behavior of the gamma ' phase. In both electrolytes, the gamma ' phase exhibits a lower surface potential than the gamma matrix, rendering it more susceptible to preferential dissolution. Under ECM conditions, inherent interfacial differences further evolve into distinct material removal mechanisms. In NaCl, the interface remains continuously activated, resulting in continuous and uniform material removal and ultimately forming a regular honeycomb-like morphology. In contrast, the strong interfacial stabilization effect in NaNO3 induces spatially asynchronous and intermittent dissolution behavior, leading to non-uniform material removal and pronounced surface undulations. Electrochemical drilling experiments demonstrate that NaCl yields a flat hole bottom and low inner-wall roughness, whereas NaNO3 results in protrusions and higher roughness. These results indicate that NaCl leads to higher surface quality in the ECM of IN939 in this study, providing theoretical support and guidance for electrolyte selection and surface quality optimization.

The low grinding force and minimal electrode wear of electrochemical grinding machining (ECGM) offer several advantages for machining thin-walled structures made of materials that are difficult to machine. In this study, we propose the application of ECGM to process high volume-fraction (63% vol.) SiCp/Al composites. The interfacial bonding strength between the matrix and the SiC particles can be weakened by preferentially dissolving the conductive Al matrix through electrochemical reactions, which reduces the grinding force and tool wear while improving the machined surface quality. Experimental results showed that the removal mechanisms of the constituent phases varied significantly with equivalent electric charge (Qeq), thereby affecting the grinding force applied and the damage to the workpiece surface. We found that Al removal shifted from mechanical grinding to electrochemical dissolution as Qeq increased, which weakened the matrix-particle bonding and facilitated the removal of SiC particles. Consequently, grinding force (23.923 N to 9.903 N), tool wear (0.7 mg to 0.2 mg), and subsurface damage thickness (16 mu m to 9.5 mu m) decreased. Finally, we fabricated TR shell structures with an average wall thickness of 1.4 mm using the proposed approach, along with ultra-thin-walled structures with a minimum thickness of 0.503 mm and low surface damage.

The ion thruster represents one of the most extensively utilized electric propulsion systems in aerospace applications. To effectively address the heat dissipation challenge within its discharge chamber, it is critical to design and fabricate square column arrays with flow-disturbing effects inside the double-walled cooling channels. The array structure, featuring a staggered arrangement, presents challenges to existing through-mask electrochemical machining methods due to its minimal center distance and significant lateral corrosion. This study proposed a novel two-step through-mask electrochemical machining(TMECM) process utilizing reusable masks including scanning TMECM and stamping TMECM. This method facilitated the creation of staggered columns by machining micro-dimples interspersed between micro-groove arrays. The formation of columns from micro-dimples on a constrained surface significantly differs from traditional machining on smooth surface. The formation process of micro-columns and micro-dimples were investigated via dynamic electric-field simulation, enabling the design of a reusable mask with I-shaped through-holes. When the micro-dimples are interconnected with the grooves, this mask can effectively intensify the electric field at the junction, thereby regulating the material removal rate at this position and enabling precise shape control of the square column. The design of the mask through-hole size was then conducted based on the simulation results. Thereafter, the effects of key machining parameters on the column formation were experimentally investigated. Using optimal parameters, we successfully fabricated over 400 staggered square columns on TC4 titanium alloy at one time. This approach permits the large-scale and efficient fabrication of micro-column arrays.

Electrochemical arc machining (ECAM) can be efficiently utilized for difficult-to-cut materials regardless of their mechanical properties. In ECAM using a non-pulse direct-current supply, arc discharges with varying energy levels are generated, among which high-energy arc discharges cause severe electrode wear and reduce machining performance. Herein, arc discharge behavior was manipulated by changing tool electrode materials and through the introduction of a regulating resistor to improve machining performance. Through the analysis of electrical signals, an equivalent circuit model was established for the electrochemical and arc discharge stages of ECAM. Based on this model, the arc discharge behavior was quantitatively characterized from three dimensions: arc discharge frequency, average arc discharge peak current, and average arc discharge sustaining time. Further, the effects of tool electrode materials and voltage on arc discharge behavior were investigated. The results indicated that the WCe electrode converted more electrical energy into arc discharge energy than W and graphite electrodes. Moreover, arc discharges generated by the WCe electrode exhibited good consistency, with approximately 93.4 % of arc discharges being within 1000-1200 A at 40 V. To limit the excessive arc discharge peak current, a 0.1 Omega regulating resistor connected in series was added into the machining circuit, thereby reducing the arc discharge peak current from 1125.75 to 210.40 A. The corresponding arc discharge transitioned from a low-frequency (<10 Hz) high-energy status to a medium-frequency (10-100 Hz) low-energy status. Owing to the decrease in the peak current of a single arc discharge, the relative electrode wear rate decreased from 2.23 % to 1.12 %, which is the lowest value reported thus far for the machining of SiCP/Al. In addition, the machining accuracy was improved, with the machined groove width being reduced from 7.100 to 6.861 mm.

In this study, a low cost laser marker fast ablation of molybdenum (Mo) coated glass substrate was adopted to fabricate superhydrophilic micro-nano structure. A hierarchical micro-nano structure with quasi-periodical hillock-hollow micron structure and widely distributed nanoparticles were shown on the treated surface, which resulted in a contact angle of 0 degrees. The treated glass showcased remarkable antifog performance without apparent degradation for over 12 months, which was an impressive record free of apparent degradation. It also exhibited apparent antifog performance with increased water contact angle (WCA) to 5.5 degrees after two weeks salt spray test, such low WCA and impressive antifog performance after such long salt spray test has not been reported before. However, the sample surface exhibited a marked decline in superhydrophilicity and antifog performance after over 15 months storage in the laboratory, which was attributed to the deposition of organic pollutants in the ambient. Thermal annealing at 400 degrees C for 1 h partially restored the antifog and super- hydrophilic properties, reducing the contact angle to 7.4 degrees. Remarkably, a one-second flame treatment fully restored the superhydrophilicity and antifog properties, which induced surface chemistry redistribution and was not reported before. Additionally, the treated glass demonstrated self-cleaning properties and enhanced broadband transmission. This brief and straightforward treatment highlights the potential of laser-ablated glass for a wide range of practical applications.

Micro-nanostructures are widely used for heat transfer, friction reduction, and drag reduction. This study proposes a new electrolyte composition and optimizes current density to fabricate concave-convex nanostructures on single-crystal superalloys. Based on the selective dissolution mechanism of gamma/gamma ' phases, two types of nanostructures are precisely formed: a grid-like structure with mildly raised gamma phases (similar to 12 nm) and wide channels (similar to 500 nm), and a columnar structure with prominently raised gamma ' phases (similar to 54 nm) and narrow channels (similar to 50 nm). The results reveal distinct electrochemical responses depending on the electrolyte and current density (0.5-20 A cm(-2)). In sodium chloride, protective elements such as Cr and W enrich in the gamma phase, making the gamma ' phase the primary dissolution pathway, whereas in sodium nitrate, the gamma phase dissolves preferentially. Water-based solutions showed high sensitivity to current density, affecting surface morphology, while glycol-based solutions exhibited reduced sensitivity, facilitating smoother, more refined nanostructures. Thus, the surface morphology can be finely tuned through electrolyte-driven selectivity. Furthermore, the resulting nanostructures provide a controllable basis for tailoring surface characteristics in single-crystal alloys.

Silicon carbide particle-reinforced aluminum matrix (SiCP/Al) composites are widely used in aerospace and microelectronics due to their high strength, thermal conductivity, and wear resistance. However, the presence of hard and brittle SiC particles makes them extremely difficult to machine, especially at medium to high volume fractions. To address this challenge, electrochemical mill-grinding (ECMG)—a hybrid process integrating electrochemical milling and mechanical grinding using an abrasive tool electrode—was employed for the efficient machining of 45 vol

Silicon carbide particle-reinforced aluminum matrix (SiCp/Al) is a composite material that is difficult to machine, particularly at high volume fractions. This study investigated the feasibility and stability of machining high volume fraction SiCp/Al using electrochemical milling-grinding (ECMG). Unstable electrochemical discharge machining (ECDM) can easily occur during traditional vertical plunge ECMG. Burn marks were observed on the machined surface, and energy-dispersive X-ray spectroscopy detected the presence of tool electroplating materials such as Ni and Cu on the workpiece, implying tool material adhesion. Modeling and simulations of the electrolyte flow field during the ECMG process demonstrated the critical role of electrolyte convection in material removal. A slow electrolyte flow velocity allowed machining debris and heat to build up in the machining gap, creating favorable conditions for abnormal discharge and material removal via ECDM. Therefore, the tool trajectory was modified from the original vertical plunge cut followed by horizontal cutting to an angled cut followed by reversed horizontal cutting. Simulation results indicated that the modified tool trajectory improved electrolyte flow field uniformity and velocity in the machining gap. Consequently, the electrolyte in the machining gap was continuously refreshed, leading to a stable ECMG process that was confirmed by the electrical signals collected from the power supply during machining. Finally, the voltage, cutting depth, and feed rate parameters were optimized to increase the grinding effect and machining efficiency, thereby improving the surface quality of the machined material. A 90 mm x 25 mm plane SiCp/Al specimen with a volume fraction of 63 % was successfully processed using the modified trajectory with the optimal parameters.

Deep holes with high quality are extensively demanded in such industrial applications as aviation. Electrochemical drilling (ECD) is a promising technique for fabricating deep holes in difficult-to-machine materials. However, at the initial machining stage, the electrolyte flow in the inter-electrode gap changes dramatically from expansion flow to converging flow, which may affect the machining process. To address this, a leading flow structure is developed to confine the electrolyte flow when machining the hole entrance, which helps to improve processing stability. A height of 10.0 mm for the leading flow structure is found to be sufficient for ensuring the fine entrance profile and machining stability. Furthermore, the normal tube electrode commonly causes misdistribution of electrolyte flow and current density at the hole bottom, generating defects such as spikes and striations, which limits its application in deep holes requiring a flat bottom. Therefore, a combinatorial tube electrode is proposed to enhance the distribution of flow and electric fields by changing the cross-section at the tube tip, resulting in a defect-free flat bottom. Based on these findings, two typical deep holes, a through hole and a flat-bottomed blind hole, were successfully fabricated with high quality, as so the machining capability and processing stability had been prominently enhanced.

Wire electrochemical micromachining has good technical advantages in the processing of metal material microdevices. However, because it is a special material containing insoluble solid particles, 40CrNiMoA exhibits poor processing stability, frequent ignition, and serious electrode wear. In this study, an attempt was made to promote mass transfer, reduce or even avoid abnormal discharge, and reduce electrode loss using solution ultrasonic assistance. The experimental results show the following. First, the thickness of the workpiece has a great influence on the process stability, and it is difficult to stably process 2-mm workpieces without ultrasonic assistance. Second, increasing the voltage to 32 V to increase the slit width causes stronger discharge to occur because of the increase of products and particles. Third, ultrasound assistance can improve the interelectrode flow field, promoting the smooth progress of the reaction and protecting the electrode. Fourth, the electrode rotation speed can be increased to enhance the medium exchange, but the electrode loss increases because of the decrease in electrolysis ability. Finally, a square spiral structure (with an overall length of 31 mm) was processed stably by optimizing the parameters.

Electrochemical machining (ECM) presents numerous applications in the production of aero-engine components. The effects of current density on surface quality during ECM of René 88DT in NaCl-ethylene glycol and NaNO3-aqueous solutions was investigated here. The results indicated that the René 88DT surface has lower sensitivity to current density and more homogeneous electrochemical dissolution in NaCl-glycol solution than in NaNO3-aqueous solution, which results in the suppression of stray corrosion and consistently high surface quality regardless of current density. These strengths are attributed that C2H5O2- and Cl- ions replace OH– ions and combine with alloy ions to form solubles and complexes, which prevent the formation of obstructive passive film, oxide layer, and insoluble electrolytic products. The electrochemical dissolution model in two solutions was established. Furthermore, the high tensile strength and precision machinability of René 88DT in NaCl-glycol solution were also demonstrated.

Efficient and cost-effective manufacturing of turbine slots has always been a challenge for aeroengine production. Wire electrochemical machining (WECM) is a feasible alternative because of its inherent characteristics. However, it readily leads to profile errors because of the uneven material removal that results from an inconsistent electric quantity when trimming complex profiles in an equidistant offset. To improve the machining accuracy of WECM for trimming turbine slots, this study proposes an electric-quantity manipulation strategy that regulates the trimming velocity of wire electrodes to facilitate equal material removal for complex profiles. The evolution of complex profiles was revealed through simulation, which led to the derivation of profile shapedependent, regulated trimming velocities that enabled an equal electric quantity and amount of material removal. Subsequently, the electric quantity distribution, material-removal depth, and profile deviation of the turbine slot structure with and without the manipulation strategy were compared through simulations and experiments. The surface integrity of the machined turbine slots was verified. The experimental results indicate that the WECM trimming technique with the manipulating strategy prevents overcutting at convex arcs and undercutting at concave arcs, reduces the overall profile deviation of the turbine slot from +50 to +18 mu m, and reduces the deviation of the mortise-tenon contact surface from +30.7 to +3.6 mu m compared to that without the manipulating strategy. The fir-tree turbine slots were prepared efficiently and precisely via one-pass WECM trimming. The equalizing electric quantity strategy effectively improves the machining accuracy of WECM trimming for a complex profile.

Electrochemical drilling (ECD) offers excellent potential for processing deep holes because it does not wear tools, does not create a remelting layer on the machined surface, and does not produce residual stress during machining. However, a normal single-hole tube electrode easily forms a spike at the bottom of the drilling hole, thereby destroying the flatness at the bottom. This phenomenon is clearly visible when drilling blind holes with large diameters. In this study, a tube electrode with multiple outlet holes is proposed to eliminate the spike and improve the flatness at the bottom of the hole. Specifically, a single outlet hole was discretized into multiple small-diameter outlet holes. The effects of the arrangement of the outlet holes on the electric field distribution over the workpiece surface and the flow field distribution in the machining gap were numerically investigated. The results generated according to the electric field showed that the outlet holes should be as small as possible and appropriately overlap to flatten the surface. The results generated according to the flow field indicated that increasing the number of outlet holes and their overlap ratio increased the electrolyte flow rate, but it also caused the flow fields to interfere with each other, resulting in an uneven distribution. Different tools were experimentally verified using stainless steel 20Cr13, and the stability of the process and machining quality were analyzed. The results showed that, for the given test parameters, higher machining quality and processing stability were obtained using a tool with 16 non-overlapping outlet holes. Furthermore, the discrete tube electrode was optimized using chamfered outlet holes. For a voltage of 25 V, feed speed of 0.8 mm/min, and electrolyte pressure of 0.2 MPa, a deep blind hole with a diameter of 22.43 ± 0.04 mm and depth of 71.28 mm was machined using the optimal tool, which had a roundness of 0.0201 mm, flatness of 52.46 µm, and taper of 0.1296°.