Search Results (92)

Electropolishing is an essential process for the surface treatment of metallic materials. To determine the appropriate replacement timing of electropolishing solutions for their efficient use and improved productivity, it is important to periodically analyze the amounts of dissolved metals in the solutions. However, these solutions are typically highly corrosive, and on-site analytical techniques that can be easily applied at production sites have not yet been established. In this study, we demonstrated microvolume liquid analysis using low-energy laser-induced breakdown spectroscopy (LIBS) combined with a porous silicon substrate fabricated by metal-assisted etching (metal-assisted chemical etching) and a non-contact gas-blowing pretreatment. In the analysis of electropolishing solutions used for niobium superconducting cavities and stainless steel products, emission lines of niobium and of iron and chromium were successfully detected after blowing the respective microdroplet samples on porous silicon, and linear correlations were observed between the spectral line intensity and the polished amounts. The present results provide a basis for future on-site application of LIBS to highly corrosive electropolishing solutions in the metal finishing industry. Full article

Purpose: The increasing demand for alternatives to autologous and resorbable bone grafts in the treatment of bone defects is driving research efforts. This study aims to evaluate the effects of different surface treatments on zinc-1%-magnesium (Zn-1Mg) alloy scaffolds on chondrocytes and osteoblasts, focusing on cytotoxicity, biocompatibility, and cell proliferation. Methods: Zn-1Mg alloy disks were manufactured additively by the powder bed fusion of metals using a laser beam (PBF-LB/M) and underwent different distinct surface treatments, including as-built treatment, sandblasting, Zn-1Mg-blasting, and electropolishing, respectively. Chondrocytes and osteoblasts were cultured separately on these additively manufactured Zn-1Mg alloy disks for 3, 7, and 14 days to assess biocompatibility and cellular growth. Cell viability, cytotoxicity, and proliferation were analyzed using DAPI staining, live/dead staining, fluorescence microscopy, and flow cytometry. Additionally, cellular morphology was investigated using Phalloidin/DAPI staining and scanning electron microscopy (SEM). Zn-1Mg scaffolds were also manufactured and subjected to the same surface treatments. All aforementioned experiments were repeated using Zn-1Mg scaffolds with co-cultured osteoblasts and chondrocytes. Results: All samples, irrespective of the surface treatment, showed similar effects compared to the reference surfaces in terms of cell viability, cytotoxicity, and proliferation for both chondrocytes and osteoblasts. SEM analysis revealed comparable cellular morphology across all scaffolds, with cells observed attaching and growing on all scaffold surfaces. This indicates that all scaffolds independent of different surface treatments exhibit good biocompatibility. Conclusions: The findings indicate that Zn-1Mg alloy samples with different surface treatments exhibit no significant differences in cytocompatibility with chondrocytes and osteoblasts. Zn-1Mg alloy scaffolds, composed of 99% zinc and 1% magnesium, demonstrate biocompatibility, with cells attaching and growing on all scaffold surfaces. These results suggest that Zn-1Mg alloy scaffolds manufactured additively by PBF-LB/M hold promise for use in resorbable bone graft applications. Full article

The study investigates the effect of plasma-electrolytic polishing on the structure and wear resistance of 30KhGSA steel after plasma-electrolytic boriding. Plasma-electrolytic boriding was carried out in a boron-containing electrolyte at a temperature of 900 °C, which ensured the formation of a hardened modified layer consisting of a surface oxide layer, a subsequent zone composed of boride phases FeB and Fe₂B, as well as a transitional martensitic zone. To remove brittle oxide phases and reduce surface roughness, plasma-electrolytic polishing in an alkaline solution was applied, which made it possible to form a smoother and more stable surface. The results showed that plasma-electrolytic boriding increases the microhardness up to 1500–1600 HV_0.1, which is 5–6 times higher compared to untreated steel, and reduces the friction coefficient and wear rate. However, the borided layers exhibit brittleness and surface roughness. Subsequent plasma-electrolytic polishing made it possible to reduce surface roughness by nearly an order of magnitude, decrease the friction coefficient by more than 30%, and almost halve the wear rate. The obtained results confirm the high potential of this combined technology for strengthening structural steel components operating under high loads and severe wear conditions. Full article

The advent of the additive manufacturing of Ti-6Al-4V (Ti64) alloys has facilitated the production of complex geometries for various industrial applications. Nevertheless, the inherent surface roughness of selective laser melting (SLM)-produced parts remains a critical limitation, adversely affecting fatigue life, wear, corrosion, and compliance with stringent surface quality standards, for example those required in hygienic applications. Conventional post-processing methodologies, encompassing grinding and electropolishing, are frequently multi-stage, labor-intensive, and reliant on hazardous electrolytes, which thus limits their use for certain applications. In this study, plasma electrolytic polishing (PEP) was evaluated as a single-step finishing process for 3D-printed Ti64 components. The findings indicate that PEP efficiently diminished surface roughness from initial values of approximately 9–10 µm to as low as 0.38–0.5 µm within a time frame of 15–20 min, depending on the initial surface condition. These outcomes meet hygienic surface requirements while ensuring the use of environmentally compatible electrolytes. The findings establish PEP as a non-mechanical, efficient, and scalable additive-manufacturing post-processing strategy. It has the capacity to supersede conventional multi-stage workflows and offer substantial reductions in cost, time, and environmental impact. Full article

The design and production of goods have been completely transformed by additive manufacturing (AM), which makes it possible to create components with intricate and complex geometries that were previously impossible or impractical to produce. However, current technologies continue to produce coarse-surfaced metal components that typically exhibit fatigue properties, resulting in component failure and unfavorable friction coefficients on the printed part. Therefore, to improve the surface quality of the fabricated parts, post-processing of AM-created components is required. With emphasis on electroless nickel plating, ChemPolishing (CP), and ElectroPolishing (EP), this study investigates post-processing methods for stainless steel that is additively manufactured (AM). The rough surfaces created by additive manufacturing (AM) restrict direct use. While ElectroPolishing (EP) achieves high material removal rates but may not be consistent, ChemPolishing (CP) offers uniform smoothening. Nickel plating enhances additive manufacturing (AM) products’ resistance to wear and scratches and corrosion protection. To optimize nickel deposition, medium (6%–9%) and high (10%–13%) phosphorus nickel was tested using the L9 Taguchi design of experiments (DOE). Mechanical properties, including scratch resistance and adhesion, were evaluated using the TABER 5900 reciprocating (Taber Industries, North Tonawanda, NY, USA) abraser apparatus, a 5 N scratch test, and ASTM B-733 thermal shock method. Surface analysis was performed with the KEYENCE VHX-7000 microscope (Keyence Corporation, Itasca, IL, USA), and chemical composition before and after nickel deposition was assessed via the ThermoFisher Phenom XL scanning electron microscope (SEM, Thermo Fisher Scientific, Waltham, MA, USA) Optimal processing conditions, determined using Qualitek-4 software, Version 20.1.0 revealed improvements in both surface finish and mechanical robustness. This comprehensive analysis underscores the potential of nickel-coated additive manufacturing (AM) parts for enhanced performance, offering a pathway to more durable and efficient additive manufacturing (AM) applications. Full article

Plasma Electrolytic Polishing (PEP) is an advanced anodic process that enhances stainless steel surfaces through controlled electrochemical dissolution and plasma-mediated modification. This study demonstrates that PEP treatment of AISI 304 SS at 300 V in aqueous urea solution (3.0 wt.%)/NH₄NO₃ (0.25 wt.%) achieves remarkable improvements: surface roughness decreases by 54.6% (from 0.197 ± 0.023 μm to 0.0895 ± 0.0205 μm) with minimal mass loss (0.0035 g·cm⁻²) in just 20 min. Tafel analysis showed a 99% reduction in corrosion rate (0.00497 mm yr⁻¹) compared to untreated AISI 304 SS (0.094 mm yr⁻¹). Cyclic Potentiodynamic Polarization (CPDP) measurements indicated superior pitting resistance (E_pit = +0.423 vs. +0.486 V for PEP processing). XPS analysis elucidates the underlying mechanisms, showing a 91% increase in the Cr/Fe ratio (0.44 to 0.84) and complete transformation of surface oxides to protective Cr₂O₃ (57.34 wt.%) and Fe₃O₄ (55.88 wt.%), which collectively explain the enhanced corrosion resistance. Full article

This study investigates the thermal stability and microstructural evolution of the solid electrolyte medium used in DLyte^® dry electropolishing and dry anodizing processes. Samples were thermally aged between 30 °C and 45 °C to simulate Joule heating during industrial operation. Visual and SEM analyses revealed shape deformation and microcrack formation at temperatures above 40 °C, potentially reducing particle packing efficiency and electrolyte performance. Particle size distribution shifted from bimodal to trimodal upon aging, with an overall size reduction of up to 39.5% due to dehydration effects, impacting ionic transport properties. Weight-loss measurements indicated a diffusion-limited dehydration mechanism, stabilizing at 15–16% mass loss. Fourier transform infrared analysis confirmed water removal while maintaining the essential sulfonic acid groups responsible for ionic conductivity. In dry anodizing tests on titanium, aged electrolytes enhanced process efficiency, producing TiO₂ films with improved optical properties—color and brightness—while preserving thickness and uniformity (~70 nm). The results highlight the need to carefully control thermal exposure to maintain electrolyte integrity and ensure consistent process performance. Full article

Tungsten and tungsten alloys are widely used in important industrial fields due to their high density, hardness, melting point, and corrosion resistance. However, machining often leaves processing marks on their surface, significantly affecting the surface quality of precision components in industrial applications. Electrolytic polishing offers high efficiency, low workpiece wear, and simple processing. In this study, an electrolytic polishing method is adopted and a novel trisodium phosphate–sodium hydroxide electrolytic polishing electrolyte is developed to study the effects of temperature, voltage, polishing time, and solution composition on the surface roughness of a tungsten–nickel–iron alloy. The optimal voltage, temperature, and polishing time are determined to be 15 V, 55 °C, and 35 s, respectively, when the concentrations of trisodium phosphate and sodium hydroxide are 100 g·L⁻¹ and 6 g·L⁻¹. In addition, glycerol is introduced into the electrolyte as an additive. The calculated LUMO value of glycerol is −5.90 eV and the HOMO value is 0.40 eV. Moreover, electron enrichment in the hydroxyl region of glycerol can form an adsorption layer on the surface of the tungsten alloy, inhibit the formation of micro-pits, balance ion diffusion, and thus promote the formation of a smooth surface. At 100 mL·L⁻¹ of glycerol, the roughness of the tungsten–nickel–iron alloy decreases significantly from 1.134 μm to 0.582 μm. The electrochemical polishing mechanism of the tungsten alloy in a trisodium phosphate electrolyte is further investigated and explained according to viscous film theory. This study demonstrates that the trisodium phosphate–sodium hydroxide–glycerol electrolyte is suitable for electropolishing tungsten–nickel–iron alloys. Overall, the results support the application of tungsten–nickel–iron alloy in the electronics, medical, and atomic energy industries. Full article

In electropolishing, the material removal rate is frequently neglected, as this process is primarily focused on surface finish, and yet, it is crucial for manufacturing metallic sheets. Solutions are required to enhance the material removal rate while maintaining surface quality. This work introduces an electropolishing technique that involves suspending ethanol in an electrolyte solution and employing a magnetic field during machining processes. The Taguchi approach is utilized to determine the ideal process parameters for enhancing the material removal rate of SS 316L electropolishing through a L9 orthogonal array. Pareto analysis of variance (ANOVA) is utilized to examine the four parameters of the machining process: applied voltage, ethanol concentration, machining gap variation, and the magnetic field of the electrolyte. The results demonstrate that the applied voltage, the incorporation of ethanol in electropolishing, and a reduced machining gap significantly increase the material removal rate; however, the introduction of a magnetic field did not notably increase the material removal rate. Full article

Nb₃Sn has a superconducting transition temperature of 18.1 K and a superheating magnetic field of 420 mT, making it one of the most promising materials for superconducting radiofrequency (SRF) cavities. The surface roughness reduction and mechanical stability of Nb₃Sn films are two important issues to improve the cavity RF performance and reliability in the application of conduction-cooling accelerators. This paper presents the studies on the surface roughness of Nb₃Sn films prepared by the tin vapor diffusion method and proves the advantages of buffered electropolishing (BEP) as a pre-polishing method. The smallest mean roughness of 26 nm, with a grain size of 760 nm, was achieved by fast BEP treatment on the niobium substrate. Nb₃Sn films on flat and curved substrates with the same coating process on Nb₃Sn cavities at Peking University (PKU) were tested under different tensile and compressive stress levels. The results showed that Nb₃Sn films had severe crack risks while loading stresses, and a safe strain range of (−2.3%, 0.9%) is suggested. To study the tuning problems for Nb₃Sn cavities, 150 kHz tuning was performed on the previously obtained high-performance cavity. Full article

Biomedical alloys in general, except for the biodegradable type, exhibit passive behavior in neutral chloride solutions. Two commonly used biomedical alloys are nitinol (NiTi) and Co-35Ni-20Cr-10Mo (CoNiCrMo). In this work, the passive behavior of electropolished NiTi and CoNiCrMo in a simulated physiological solution (phosphate-buffered saline) was compared using data largely obtained from our previous studies involving potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The potentiodynamic results showed a marked difference in passive behavior between the alloys, with NiTi remaining completely passive up to the oxidation of water and CoNiCrMo, in contrast, undergoing solid-state oxidation and then transpassive dissolution. Both alloys exhibited Tafel-type behavior over the initial part of the passive range. A small but distinct difference in the apparent Tafel slopes was found between the two alloys and can be attributed to the difference in their predominant oxide; that is, TiO₂ versus Cr₂O₃. The EIS results also showed marked differences between the alloys in terms of the oxide thickness and resistivity. The thickness was greater for NiTi—consistent with surface analytical results—and differed in potential dependence between the two alloys in the passive region. The oxide resistivity, conversely, was substantially lower for NiTi and showed a similar potential dependence for the two alloys. Full article

Mechanically flexible substrates are increasingly utilized in electronics and advanced energy technologies like solar cells and high-temperature superconducting coated conductors (HTS-CCs). These substrates offer advantages, such as large surface areas and reduced manufacturing costs through reel-to-reel processing, but often lack the surface smoothness needed for optimal performance. For HTS-CCs, specific orientation and high crystalline quality are essential, requiring buffer layers to prepare the amorphous substrate for superconductor deposition. Techniques, such as mechanical polishing, electropolishing, and chemical-mechanical polishing, can help achieve an optimally levelled surface suitable for the subsequent steps of sputtering and ion-beam-assisted deposition (IBAD) necessary for texturing. This review examines Solution Deposition Planarization (SDP) as a cost-effective alternative to traditional electro-mechanical polishing for HTS coated conductors. SDP achieves surface roughness levels below 1 nm through multiple oxide layer coatings, offering reduced production costs. Comparative studies demonstrate planarization efficiencies of up to 20%. Ongoing research aims to enhance SDP’s efficiency for industrial applications in CC production. Full article

Austenitic stainless steels are used widely in many fields due to their good mechanical properties and high resistance to corrosion. This work focuses on the reconstruction of the passive film after scratching. The purpose of the study was to compare changes in the rate of passive layer reconstruction and to discuss the effect of both the type of material and its electrochemical treatment on the reconstruction of the passive layer for two types of stainless steel: 304 and 316. The XPS tests performed indicate a significantly higher Cr/Fe ratio for the samples after the electropolishing process of 1.41–1.88 compared to the as-received samples of 0.82–0.86. After 2–3 min of sputtering the surface with Ar+ ions, a decrease in chromium content can be observed, with a simultaneous increase in nickel content, visible especially for the electropolished samples. A new approach in the conducted research was to scratch the test samples under controlled conditions, then evaluate the dynamics of the passive layer reconstruction using the AFM method, and then confront the obtained results with XPS measurements for the corresponding samples. For the as-received samples (2B finish) and those after surface treatment, regardless of the level of contamination of the electropolishing process bath, the reconstruction time was similar, which was approximately 2 h, although certain differences in the process dynamics were noticeable. Full article

This study systematically compares the surface polishing performance and finishing results of the following two different electrolytic plasma polishing technologies on stainless steel AISI 316L: (i) plasma electrolytic polishing (PEP) and (ii) plasma electrolytic polishing jet (PEP-Jet). The two techniques are compared against an industrial standard polishing method, electropolishing (EP). For comparable energy density consumption, the samples treated with the PEP-Jet technique showed the highest removal rate, up to three times less than the initial roughness, resulting in the highest surface roughness reduction from Sa = 249 nm to Sa = 81 nm. Microstructure characterization of samples treated using PEP-Jet also showed well-defined crystalline grain boundaries with a distinct appearance of predominantly inter-crystalline structures within individual grains, which is uncommon with EP techniques. The surfaces treated using PEP-Jet exhibited the lowest corrosion rate of $6.79\times {10}^{-5}$ mm/year, and no signs of areal corrosion were detected in the performed corrosion tests in contrast with the other samples and their respective treatments. The comparative analysis revealed that the high ionic current delivered by the electrolyte jet flow in the PEP-Jet process effectively stabilizes the plasma at the contact zone, thereby enhancing the plasma polishing of austenitic stainless steel samples. The efficacy of this method has been demonstrated in terms of reducing energy consumption and enhancing corrosion resistance in comparison with (PEP) and (EP) as state-of-the-art processes in corrosive environments of high-alloyed steel. Full article

Post-processing, and particularly the dry electropolishing process, is essential for improving the surface quality of 3D-printed Ti6Al4V samples, with specific emphasis on reducing roughness over extended polishing times while preserving mechanical properties. Reducing surface roughness enhances the reliability of hardness measurements and improves the consistency of elastic modulus measurements, as prolonged polishing time stabilizes the full width at half maximum values, thereby minimizing variability due to uniaxial indentation. This stability is crucial for maintaining the structural integrity and uniformity of mechanical properties, facilitating better performance and reliability in biomedical applications. Additionally, under service-like working conditions, solid electrolyte particles undergo dehydration due to the Joule effect, introducing a dynamic aspect to the system as the particle structure degrades with thermal cycling. EDX cross-sectional analysis reveals that TiO₂ informs the particle’s surface, with an oxygen-to-titanium ratio that confirms the oxide’s composition. This TiO₂ oxide layer demonstrates the progressive surface oxidation occurring under the post-processing process, further modifying the particle’s surface chemistry. This dual effect of roughness reduction and controlled surface chemistry highlights the role of dry electropolishing in enhancing the functional lifespan and mechanical reliability of Ti6Al4V components. Full article