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Fengzhou Fang - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Electropolishing characteristics of tungsten in eco-friendly sodium hydroxide aqueous solution
Advances in manufacturing, 2020Co-Authors: Wei Han, Fengzhou FangAbstract:In this study, an eco-friendly electrolyte for Electropolishing tungsten and the minimum material removal depth on the electropolished tungsten surface are investigated using an electrochemical etching method. Using a concentrated acid electrolyte, the polarization curve and current density transient are observed. For a NaOH electrolyte, the effects of interelectrode gap and electrolyte concentration on Electropolishing are investigated. The differences in Electropolishing characteristics are compared among different electrolyte types. Microholes are etched on the electropolished tungsten surface to determine the minimum material removal depth on the tungsten surface. Experimental results indicate the color effect due to a change in the thickness of the oxide film on the tungsten surface after Electropolishing with a concentrated acid electrolyte. The surface roughness decreases with the interelectrode gap width owing to the increased current density when using the NaOH electrolyte. However, the Electropolishing effect is less prominent with a significantly smaller gap because the generated bubbles are unable to escape from the narrow working gap in time. A material removal depth of less than 10 nm is achieved on the tungsten surface in an area of diameter 300 µm, using the electrochemical etching method.
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Investigation of electrochemical properties of Electropolishing Co–Cr dental alloy
Journal of Applied Electrochemistry, 2020Co-Authors: Wei Han, Fengzhou FangAbstract:Electropolishing is a promising method for the post-treatment of the dental material Co–Cr alloy compared with the currently reported laser polishing by considering the damage-free surface and simplicity of the Electropolishing method. The electrochemical properties of Electropolishing the Co–Cr dental alloy is a critical issue in the process development. The electrochemical properties are first investigated by measuring the open circuit potential and the polarization curves and a limiting current density plateau region is identified, where the Electropolishing is clarified. With the different applied potentials along the limiting current density plateau region, the electrochemical impedance spectroscopy spectra are studied to understand the mass transport limitation mechanism. The compact salt film model is confirmed to be responsible for the mass transport limitation in the Electropolishing. Samples are electropolished with a constant applied potential, and a selective dissolution is achieved between the matrix phase and precipitate phase according to the electropolished surface topography. Moreover, the composition of the electropolished surface is analysed by the X-ray photoelectron spectroscopy spectra. Finally, a qualitative model is established to illustrate the electrochemical dissolution behaviour of the Co–Cr alloy Electropolishing in the phosphoric acid-containing electrolyte.
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Two-step Electropolishing of 316L stainless steel in a sulfuric acid-free electrolyte
Journal of Materials Processing Technology, 2020Co-Authors: Wei Han, Fengzhou FangAbstract:Abstract The study is to electropolish 316 L stainless steel in a sulfuric acid-free electrolyte, consisting of phosphoric acid, glycerol and distilled water instead of the widely used sulfuric acid-based electrolyte. The influence of water concentration in the electrolyte on the Electropolishing characteristics was investigated from the polarization curve, material removal rate and surface roughness Ra. It is confirmed that the limiting current density increases with increasing the water concentration, resulting in a high material removal rate. However, the surface roughness Ra increases because the Electropolishing effect is lowered. The surface characteristics were analysed by X-ray photoelectron spectroscopy, and the mechanical properties were studied by nanoindentation. A two-step Electropolishing method was proposed to enhance the Electropolishing efficiency significantly by utilizing the Electropolishing characterizations with different water concentrations. The method contains two Electropolishing processes in high and low water concentration electrolyte, respectively. The experimental results show that the material removal rate is increased significantly compared with the one-step Electropolishing method with a low water concentration, and the surface roughness is decreased obviously compared with the one-step Electropolishing method with a high water concentration.
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Eco-friendly NaCl-based electrolyte for Electropolishing 316L stainless steel
Journal of Manufacturing Processes, 2020Co-Authors: Wei Han, Fengzhou FangAbstract:Abstract Since the environmental and safety issues closely related to the widely used mixture electrolytes of H2SO4 and H3PO4 in Electropolishing 316 L stainless steel, the development of new electrolytes, which do not contain any acid is of a great demand. This study is to electropolish 316 L stainless steel in a NaCl-based electrolyte, not containing any acid as the conventionally used electrolytes. The Electropolishing effect with the NaCl-based electrolyte is compared with the conventional H2SO4-based electrolyte. The experimental results show that the proposed electrolyte can be used for the Electropolishing of 316 L stainless steel to obtain a comparable Electropolishing effect with the conventional H2SO4-based electrolyte. Moreover, the NaCl-based electrolyte shows a higher material removal rate than the H2SO4-based electrolyte. It is also found that a brown product generated and covered on the anode electrode surface during the Electropolishing with the NaCl-based electrolyte. According to the EDS analysis, it mainly contains dissolved metal elements, Cl and Na element from the used electrolyte. Furthermore, the Electropolishing effect can be improved by the ethanol addition in the NaCl-based electrolyte due to the reduced influence of the brown product.
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Electropolishing of 316L Stainless Steel Using Sulfuric Acid-Free Electrolyte
Journal of Manufacturing Science and Engineering, 2019Co-Authors: Wei Han, Fengzhou FangAbstract:Abstract The study is to investigate the Electropolishing characteristics of 316L stainless steel in a sulfuric acid-free electrolyte of phosphoric acid and glycerol and to explore the possibility of using this eco-friendly electrolyte instead of the widely used sulfuric acid-based electrolyte. The influences of process parameters on polishing effects and the corrosion resistance of electropolished samples are investigated. The experimental results show that the Electropolishing temperature and acid concentration are directly related to the mass transport mechanism in the limiting current plateau region. The grain boundaries of workpiece were electrochemically dissolved faster than the grain themselves at the beginning of the Electropolishing process because they are more reactive than grains. Moreover, the conventional sulfuric—phosphoric acid electrolyte was also used to electropolish the 316L stainless steel, and the electropolished surfaces were compared with the sulfuric acid-free electrolyte proposed in this study. When the sulfuric acid-free electrolyte was used to electropolish the 316L stainless steel, the X-ray photoelectron spectroscopy (XPS) analysis shows that atomic Cr/Fe ratio of 316L stainless steel was increased from 0.802 to 1.909 after Electropolishing process in the sulfuric acid-free electrolyte of phosphoric acid and glycerol. The corrosion resistance of the electropolished 316L stainless steel is studied using electrochemical analysis, and the results are verified experimentally.
Wei Han - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Electropolishing characteristics of tungsten in eco-friendly sodium hydroxide aqueous solution
Advances in manufacturing, 2020Co-Authors: Wei Han, Fengzhou FangAbstract:In this study, an eco-friendly electrolyte for Electropolishing tungsten and the minimum material removal depth on the electropolished tungsten surface are investigated using an electrochemical etching method. Using a concentrated acid electrolyte, the polarization curve and current density transient are observed. For a NaOH electrolyte, the effects of interelectrode gap and electrolyte concentration on Electropolishing are investigated. The differences in Electropolishing characteristics are compared among different electrolyte types. Microholes are etched on the electropolished tungsten surface to determine the minimum material removal depth on the tungsten surface. Experimental results indicate the color effect due to a change in the thickness of the oxide film on the tungsten surface after Electropolishing with a concentrated acid electrolyte. The surface roughness decreases with the interelectrode gap width owing to the increased current density when using the NaOH electrolyte. However, the Electropolishing effect is less prominent with a significantly smaller gap because the generated bubbles are unable to escape from the narrow working gap in time. A material removal depth of less than 10 nm is achieved on the tungsten surface in an area of diameter 300 µm, using the electrochemical etching method.
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Investigation of electrochemical properties of Electropolishing Co–Cr dental alloy
Journal of Applied Electrochemistry, 2020Co-Authors: Wei Han, Fengzhou FangAbstract:Electropolishing is a promising method for the post-treatment of the dental material Co–Cr alloy compared with the currently reported laser polishing by considering the damage-free surface and simplicity of the Electropolishing method. The electrochemical properties of Electropolishing the Co–Cr dental alloy is a critical issue in the process development. The electrochemical properties are first investigated by measuring the open circuit potential and the polarization curves and a limiting current density plateau region is identified, where the Electropolishing is clarified. With the different applied potentials along the limiting current density plateau region, the electrochemical impedance spectroscopy spectra are studied to understand the mass transport limitation mechanism. The compact salt film model is confirmed to be responsible for the mass transport limitation in the Electropolishing. Samples are electropolished with a constant applied potential, and a selective dissolution is achieved between the matrix phase and precipitate phase according to the electropolished surface topography. Moreover, the composition of the electropolished surface is analysed by the X-ray photoelectron spectroscopy spectra. Finally, a qualitative model is established to illustrate the electrochemical dissolution behaviour of the Co–Cr alloy Electropolishing in the phosphoric acid-containing electrolyte.
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Two-step Electropolishing of 316L stainless steel in a sulfuric acid-free electrolyte
Journal of Materials Processing Technology, 2020Co-Authors: Wei Han, Fengzhou FangAbstract:Abstract The study is to electropolish 316 L stainless steel in a sulfuric acid-free electrolyte, consisting of phosphoric acid, glycerol and distilled water instead of the widely used sulfuric acid-based electrolyte. The influence of water concentration in the electrolyte on the Electropolishing characteristics was investigated from the polarization curve, material removal rate and surface roughness Ra. It is confirmed that the limiting current density increases with increasing the water concentration, resulting in a high material removal rate. However, the surface roughness Ra increases because the Electropolishing effect is lowered. The surface characteristics were analysed by X-ray photoelectron spectroscopy, and the mechanical properties were studied by nanoindentation. A two-step Electropolishing method was proposed to enhance the Electropolishing efficiency significantly by utilizing the Electropolishing characterizations with different water concentrations. The method contains two Electropolishing processes in high and low water concentration electrolyte, respectively. The experimental results show that the material removal rate is increased significantly compared with the one-step Electropolishing method with a low water concentration, and the surface roughness is decreased obviously compared with the one-step Electropolishing method with a high water concentration.
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Eco-friendly NaCl-based electrolyte for Electropolishing 316L stainless steel
Journal of Manufacturing Processes, 2020Co-Authors: Wei Han, Fengzhou FangAbstract:Abstract Since the environmental and safety issues closely related to the widely used mixture electrolytes of H2SO4 and H3PO4 in Electropolishing 316 L stainless steel, the development of new electrolytes, which do not contain any acid is of a great demand. This study is to electropolish 316 L stainless steel in a NaCl-based electrolyte, not containing any acid as the conventionally used electrolytes. The Electropolishing effect with the NaCl-based electrolyte is compared with the conventional H2SO4-based electrolyte. The experimental results show that the proposed electrolyte can be used for the Electropolishing of 316 L stainless steel to obtain a comparable Electropolishing effect with the conventional H2SO4-based electrolyte. Moreover, the NaCl-based electrolyte shows a higher material removal rate than the H2SO4-based electrolyte. It is also found that a brown product generated and covered on the anode electrode surface during the Electropolishing with the NaCl-based electrolyte. According to the EDS analysis, it mainly contains dissolved metal elements, Cl and Na element from the used electrolyte. Furthermore, the Electropolishing effect can be improved by the ethanol addition in the NaCl-based electrolyte due to the reduced influence of the brown product.
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Electropolishing of 316L Stainless Steel Using Sulfuric Acid-Free Electrolyte
Journal of Manufacturing Science and Engineering, 2019Co-Authors: Wei Han, Fengzhou FangAbstract:Abstract The study is to investigate the Electropolishing characteristics of 316L stainless steel in a sulfuric acid-free electrolyte of phosphoric acid and glycerol and to explore the possibility of using this eco-friendly electrolyte instead of the widely used sulfuric acid-based electrolyte. The influences of process parameters on polishing effects and the corrosion resistance of electropolished samples are investigated. The experimental results show that the Electropolishing temperature and acid concentration are directly related to the mass transport mechanism in the limiting current plateau region. The grain boundaries of workpiece were electrochemically dissolved faster than the grain themselves at the beginning of the Electropolishing process because they are more reactive than grains. Moreover, the conventional sulfuric—phosphoric acid electrolyte was also used to electropolish the 316L stainless steel, and the electropolished surfaces were compared with the sulfuric acid-free electrolyte proposed in this study. When the sulfuric acid-free electrolyte was used to electropolish the 316L stainless steel, the X-ray photoelectron spectroscopy (XPS) analysis shows that atomic Cr/Fe ratio of 316L stainless steel was increased from 0.802 to 1.909 after Electropolishing process in the sulfuric acid-free electrolyte of phosphoric acid and glycerol. The corrosion resistance of the electropolished 316L stainless steel is studied using electrochemical analysis, and the results are verified experimentally.
Hong Hocheng - One of the best experts on this subject based on the ideXlab platform.
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The application of a turning tool as the electrode in Electropolishing
Journal of Materials Processing Technology, 2002Co-Authors: Hong HochengAbstract:Abstract In the current study, Electropolishing using a turning tool as the electrode for several die materials following turning is investigated. The proposed method uses a traveling electrode instead of the mating electrode as in conventional ECM, hence the dimensional error can be controlled more effectively. Further, the method removes a certain limited amount of material, therefore the complex pre-polishing as required in the soakage Electropolishing method is eliminated. This process can be used for various turning operations including end turning, form turning, and flute and thread cutting. Through the attachment of simple equipment, Electropolishing can follow the cutting on the same machine and chuck. The electrode of the turning tool travels and polishes the machined surface of workpiece with electrical current. Among the factors affecting the Electropolishing, the design of tool electrode is discussed primarily. A common turning tool can be used in Electropolishing, while a slight modification of tool geometry achieves optimal polishing at low cost. The controlling factors include the chemical composition and concentration of the electrolyte, the initial gap width, and the flow rate of the electrolyte. The experimental parameters are the current rating, the electrode geometry, the die material, the workpiece rotational speed, and the electrode feed rate. Turning tools with larger angles and smaller cross-section are associated with larger discharge space and thus polish better. The most significant factors in tool design for improving the surface roughness include the end clearance angle and the end cutting edge angle. A smaller nose radius is associated with higher current density and provides a faster feed rate and a better polishing effect.
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The application of a turning tool as the electrode in Electropolishing
Journal of Materials Processing Technology, 2002Co-Authors: Hong HochengAbstract:[[abstract]]In the current study, Electropolishing using a turning tool as the electrode for several die materials following turning is investigated. The proposed method uses a traveling electrode instead of the mating electrode as in conventional ECM, hence the dimensional error can be controlled more effectively. Further, the method removes a certain limited amount of material, therefore the complex pre-polishing as required in the soakage Electropolishing method is eliminated. This process can be used for various turning operations including end turning, form turning, and flute and thread cutting. Through the attachment of simple equipment, Electropolishing can follow the cutting on the same machine and chuck. The electrode of the turning tool travels and polishes the machined surface of workpiece with electrical current. Among the factors affecting the Electropolishing, the design of tool electrode is discussed primarily. A common turning tool can be used in Electropolishing, while a slight modification of tool geometry achieves optimal polishing at low cost. The controlling factors include the chemical composition and concentration of the electrolyte, the initial gap width, and the flow rate of the electrolyte. The experimental parameters are the current rating, the electrode geometry, the die material, the workpiece rotational speed, and the electrode feed rate. Turning tools with larger angles and smaller cross-section are associated with larger discharge space and thus polish better. The most significant factors in tool design for improving the surface roughness include the end clearance angle and the end cutting edge angle. A smaller nose radius is associated with higher current density and provides a faster feed rate and a better polishing effect. © 2002 Elsevier Science B.V. All rights reserved.[[fileno]]2020212010003[[department]]動機
E. Stijns - One of the best experts on this subject based on the ideXlab platform.
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Electropolishing of Copper in H3PO4 Ex Situ and In Situ Optical Characterization
Journal of The Electrochemical Society, 2007Co-Authors: S. Van Gils, C. Le Pen, A. Hubin, Herman Terryn, E. StijnsAbstract:Electropolishing copper in 14 M H 3 PO 4 was studied using both ex situ and in situ optical techniques. First, an ex situ study revealed the influence of the Electropolishing potential on the visual appearance and the surface topography. Gloss together with total integrated scattering reflected the changes in surface roughness as evidenced from optical profilometry images. Second, an in situ optical study using ellipsometry revealed the changes in the thickness of the surface film, as well as roughness modifications. Altogether, this provided the characterization of the whole Electropolishing process in terms of roughness and film formation. From the polarization curve combined with the complementary analysis techniques it was observed in situ that an initial regime showed increased roughness of the copper surface, followed by a current limiting plateau exhibiting the best conditions of Electropolishing: anodic brightening. For higher applied potentials, a region with pitting and deterioration of the appearance followed.
Tadeusz Hryniewicz - One of the best experts on this subject based on the ideXlab platform.
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xps depth profiling analysis of passive surface layers formed on austenitic aisi 304l and aisi 316l ss after high current density Electropolishing
Surface & Coatings Technology, 2015Co-Authors: Krzysztof Rokosz, Tadeusz Hryniewicz, Jouko Lahtinen, Slawomir RzadkiewiczAbstract:Abstract In this paper, the XPS depth profiling results of passive surface layers formed on nickel–chromium AISI 304L and nickel–chromium–molybdenum AISI 316L austenitic stainless steels after a standard Electropolishing at current density of 50 A/dm 2 (EP50), and after a high current density Electropolishing at 1000 A/dm 2 (EP1000) in the mixture of sulfuric/orthophosphoric acids electrolyte in the following proportions H 3 PO 4 :H 2 SO 4 = 1:4 and 4:1 are presented. The results have shown, that in case of nickel–chromium austenitic stainless steel (AISI 304L) there were no detected significant differences in the chemical composition of the passive layer formed after EP50 and EP1000 electrochemical treatments. In the passive layer of nickel–chromium–molybdenum austenitic stainless steel, the chromium and molybdenum enrichment was noted after EP1000 Electropolishing, but was not observed after EP50 operation.
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Towards a new conception of Electropolishing of metals and alloys
International Journal of Materials & Product Technology, 2014Co-Authors: Tadeusz HryniewiczAbstract:Electropolishing of metals and numerous alloys may provide, smooth, bright, and reflective surfaces that exhibit superior corrosion resistance compared to untreated metals. These features are achieved mainly in Electropolishing of pure metals and single–phase alloys. Past works have indicated that in comparison with different treatments (mechanical polishing, chemical etching), Electropolishing produces much thinner surface layer of changed properties. That implies a difference in the surface chemistry which is valuable from the viewpoint of the technical usefulness of such surfaces. Experimental investigations carried out on various metals and alloys prove that both electrochemical and hydrodynamic conditions are responsible for the positive results to obtain in the process. The aim of the work is to reveal a new conception of Electropolishing covering the phenomena of diffusion, adsorption, as well as the hydrodynamic conditions.
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enhanced oxidation dissolution theory of Electropolishing
Transactions of The Institute of Metal Finishing, 2012Co-Authors: Ryszard Rokicki, Tadeusz HryniewiczAbstract:AbstractElectropolishing is the electrolytic metal finishing process currently widely used in several high tech applications such as cardiovascular and orthopaedic body implants, pharmaceutical and semiconductor installations, superconductive niobium cavities, among others. The process provides a very clean, smooth, Beilby layer free, corrosion resistant surface. Currently, almost any metal, alloy and intermetallic compound can be electropolished, but in spite of that, we still do not have a single commonly accepted Electropolishing theory. To make it even more complicated, the Electropolishing process is constantly modified by addition of other physical agents and/or forces such as a magnetic field – magnetoElectropolishing, ultrasounds, or by changing the existing process parameters such as switching from direct to pulse current. The existing Electropolishing theories differ in many ways from each other but possess one common ingredient, namely the viscous layer. The aim of this work is to show that the...
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Enhanced oxidation–dissolution theory of Electropolishing
Transactions of the IMF, 2012Co-Authors: Ryszard Rokicki, Tadeusz HryniewiczAbstract:AbstractElectropolishing is the electrolytic metal finishing process currently widely used in several high tech applications such as cardiovascular and orthopaedic body implants, pharmaceutical and semiconductor installations, superconductive niobium cavities, among others. The process provides a very clean, smooth, Beilby layer free, corrosion resistant surface. Currently, almost any metal, alloy and intermetallic compound can be electropolished, but in spite of that, we still do not have a single commonly accepted Electropolishing theory. To make it even more complicated, the Electropolishing process is constantly modified by addition of other physical agents and/or forces such as a magnetic field – magnetoElectropolishing, ultrasounds, or by changing the existing process parameters such as switching from direct to pulse current. The existing Electropolishing theories differ in many ways from each other but possess one common ingredient, namely the viscous layer. The aim of this work is to show that the...
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Polarization characteristics of magnetoElectropolishing stainless steels
Materials Chemistry and Physics, 2010Co-Authors: Tadeusz Hryniewicz, Krzysztof RokoszAbstract:Abstract The aim of the study is to present the polarization characteristics of Electropolishing process carried out in a magnetic field (MEP—magnetoElectropolishing), in comparison with the ones obtained under standard/conventional process of Electropolishing (EP) conditions. The polarization characteristics have been considered as the most important factor in establishing effective treatment conditions. With this paper we would like to show the results of the studies concerning the effects of a magnetic field strength and Electropolishing conditions (convection, temperature) on the electrochemical polarization characteristics. Specifically the occurrence of Electropolishing EP plateau has been observed in view of optimization of magnetoElectropolishing MEP process. It has been found that, depending on the magnetic field strength, under higher potentials the current density has been growing with the increase of potential to a certain value only. Afterwards the current density remains unchanged. This behavior in the course of polarization curves obtained under high potentials has been revealed to be the effect of cyclically disclosure of sample surface and re-submerge, this resulting in the “second limiting current”.