Electrolytic Plasma Polishing Research Articles

Effect of the gas layer evolution on electrolytic plasma polishing of stainless steel

In recent years, electrolytic plasma polishing technology has attracted wide attention due to its advantages of shape adaptability, high efficiency, better precision, environmental friendliness, and non-contact polishing. However, the lack of research on the evolution mechanism of the gas layer at the anode interface restricts the improvement of the material removal mechanism and the regulation of the polishing effect. Firstly, the thermodynamic conditions of gas layer formation were analyzed based on the Clapeyron-Clausius equation, and the key parameters affecting the gas layer were identified. Secondly, the laws of voltage and electrolyte temperature on the dynamic evolution of the gas layer and its polishing effect were revealed. Additionally, the influence of the gas layer on the voltage-current characteristics was also investigated by analyzing the experimental phenomena. The results indicate that the optimal polishing effect is achieved at a voltage level of 300 V resulting in a decrease in Ra from 0.451 μm to 0.076 μm. Similarly, superior polishing results are obtained when the electrolyte temperature is 80 °C, with a decrease in Ra from 0.451 μm to 0.075 μm. This study provides theoretical guidance for the further development and application of electrolytic plasma polishing technology.

Local surface smoothness on TC4 alloy during microbubbles flow electrolytic plasma polishing: prototype rig, phenomena, and mechanism

Local surface smoothness on TC4 alloy during microbubbles flow electrolytic plasma polishing: prototype rig, phenomena, and mechanism

Optimization of electrolytic plasma polishing process and surface performance analysis for 6061 aluminum alloy

Electrolytic Plasma Polishing (EPP), an innovative technology for polishing, has been utilized to improve the surface performance of 6061 aluminum alloys. An orthogonal experimental approach was carried out to investigate the multiple factors influencing the surface quality of aluminum alloys during the polishing process. The results indicated that peaks and scratches on the surface were successfully removed after polishing, with the average roughness reduced to 0.138 μm, approximately 1/8 of the original roughness. Additionally, the EPP process enhanced the substrate's corrosion resistance and hydrophobicity. Finally, it is proposed that the mechanism of surface smoothing effect of EPP is attributed to the combined action of plasma chemical dissolution and cavitation forces peeling. This research indicates EPP as a promising finishing technique with considerable potential for enhancing the surface performance of aluminum alloys in electronic component applications.

Effect of Electrolytic Plasma Polishing on Surface Properties of Titanium Alloy

Electrolytic plasma polishing (EPPo) is an advanced metal surface finishing technology with high quality and environmental protection that has broad application prospects in the biomedical field. However, the effect of EPPo on surface properties such as corrosion resistance and the wettability of biomedical titanium alloys remains to be investigated. This paper investigated the changes in surface roughness, surface morphology, microstructure, and chemical composition of Ti6Al4V alloy by EPPo and their effects on surface corrosion resistance, wettability, and residual stress. The results showed that Ra decreased from 0.3899 to 0.0577 μm after EPPo. The surface crystallinity was improved, and the average grain size increased from 251 nm to more than 800 nm. The oxidation behavior of EPPo leads to an increase in surface oxygen content and the formation of TiO2 and Al2O3 oxide layers. EPPo can significantly improve the corrosion resistance and wettability of titanium alloy in simulated body fluid and eliminate the residual stress on the sample surface. The surface properties are enhanced not only by the reduction in surface roughness but also by the formation of a denser oxide film on the surface, changes in the microstructure, an increase in surface free energy, and the annealing effect developed during EPPo. This study can provide guidance and references for applying EPPo to biomedical titanium alloy parts.

Electrolyte component preference and surface integrity impact analysis for electrolytic plasma polishing of cobalt-chromium-molybdenum alloys

Electrolyte component preference and surface integrity impact analysis for electrolytic plasma polishing of cobalt-chromium-molybdenum alloys

The formation and stripping mechanism of oxide film on Ti6Al4V alloy surface during electrolytic plasma polishing

Due to the lack of in-depth study on the oxide film formation and stripping mechanism in the electrolytic plasma polishing (EPPo) process on valve metals, the regulation of the process parameters and polishing effect is seriously restricted, resulting in the optimization and improvement only relying on process experiments. Firstly, the formation mechanism of the oxide film was proposed based on the subsurface structure and composition analysis. Subsequently, the stripping mechanism of the oxide film was proposed by analyzing the composition of the exfoliation, the discharge phenomenon and surface evolution process. Furtherly, the role of oxide film formation and stripping in surface levelling of titanium alloy was explored and verified. Results show that an oxide film consisting of TiO2 and Al2O3 with a thickness of about 550 nm was left on the surface after EPPo. The plasma enhanced the electrochemical oxidation process, resulting in the formation of oxide film. Plasma discharge erosion in the film and electrochemical dissolution act together to strip the oxide film. The dynamic balance between formation and stripping is the key to achieving surface levelling. This work can provide theoretical guidance and technical support for EPPo on valve metals.

Electrolic plasma polishing of complex parts in magnetic field

The article discusses a new technology of electrolyte-plasma polishing (EPP) of turbomachine parts with the imposition of an external magnetic field, which improves the quality of the surface layer. The results of experimental studies of the effect of electrolytic-plasma polishing of blades made of titanium alloy VT6 with the imposition of an external magnetic field are presented, indicating the prospects of using the proposed EPP method for processing parts of complex configuration, as well as the possibility of increasing the stability of the EPP process with the introduction of a magnetic field as an additional technological factor.

Parameters optimization of electrolytic plasma polishing of austenitic stainless steel and surface performance analysis

Electrolytic plasma polishing is a new type of surface finishing technology, widely used for high-quality polishing of metals and alloys due to its excellent processability. In this paper, the austenitic stainless steel (302) is the processing material, and the electrolyte temperature, electrolyte concentration, voltage, and polishing time are used as influencing factors. The surface roughness of the material is used as the evaluation index for electrolytic plasma polishing experiments. The orthogonal experimental group is designed to obtain the best process parameters of electrolytic plasma polishing through range analysis, and the influence laws of various factors on surface roughness is studied. The property of the polished sample from the aspects of surface morphology, elemental composition, X-ray diffraction analysis, hardness changes, and corrosion resistance are characterized. The experimental results show that the surface profile of the polished sample has better consistency, and overall it is flat and smooth, with the original scratches are completely removed. The surface roughness is significantly reduced from the initial 0.3–0.076 μm. The content of Cr element has increased to a certain extent, while the content of Fe element has decreased, and surface impurities have been removed. There is no phase transition on the surface of the sample, the diffraction peak intensity significantly increases, the half width prominently decreases, the crystalline grain size increases, and the surface hardness decreases. During electrochemical test, the self-corrosion potential increases, the self-corrosion current density decreases, and the corrosion resistance of the sample surface increases.

PLASMA-ELECTROLYTIC MODIFICATION OF STEEL AND TITANIUM SURFACES BY COMBINING CATHODIC NI-TRIDING AND ANODIC POLISHING

The possibility of increasing the wear resistance of steel 45 surfaces by 19.9 times and titanium alloy VT6 by 3.6 times after cathodic electrolytic plasma nitriding in a solution of ammonium chloride and ammonia and subsequent anodic electrolyte-plasma polishing in a solution of ammonium sulfate. A positive effect on wear resistance was revealed reducing surface roughness and removing the outer part of the oxide layer using anodic electrolytic plasma polishing and increasing the hardness of the surface layer as a result of cathodic nitriding. The wear mechanism is defined as fatigue upon plastic contact and boundary friction.

Biological Corrosion Resistance and Osteoblast Response of 316LVM Polished Using Electrolytic Plasma

As electrolytic plasma polishing (EPP) offers the advantages of strong shape adaptability, high efficiency, and environmental friendliness, it has great application prospects in biomedical material processing. However, the effect of EPP on the biological performance of the treated surfaces remains unclear. In the present study, the effects of EPP on the surface roughness, micro-morphology, corrosion behavior, and cell response of 316LVM were investigated. The results revealed that the surface roughness (Ra) was reduced from 0.3108 to 0.0454 µm upon EPP, and the sharp peaks and protrusions produced as a result of mechanical grinding were removed. The corrosion current density decreased from 1.129 to 0.164 µA/cm2, while the charge transfer resistance increased from 513.3 to 17,430 kΩ·cm2, which implied that EPP treatment could significantly improve the corrosion resistance of 316LVM. Furthermore, affected by the sharp ridges on both sides of the groove, the outward spreading of osteoblasts (MC3T3-E1) on the untreated samples was inhibited, and the edges were curled. The cells grew along the direction of the mechanical processing texture on the untreated samples, while they grew randomly in all directions on the surface treated using EPP, which adversely affected the growth, spreading, and migration of the cells.

Enhancement of Corrosion Resistance for Medical Grade 316L Stainless Steel by Electrolytic Plasma Polishing

Enhancement of Corrosion Resistance for Medical Grade 316L Stainless Steel by Electrolytic Plasma Polishing

Recommendations for Electrolytic Plasma Polishing of Chromium and Titanium Alloys

Recommendations for Electrolytic Plasma Polishing of Chromium and Titanium Alloys

Снижение шероховатости поверхностей аддитивных изделий электрохимическими методами обработки

The article considers the problem of improving the quality of the product surfaces obtained by selective laser melting. The possibilities of applying the method of electrochemical and electrolytic-plasma polishing for these purposes are described. The scheme and description of the experimental setup are given, as well as data on the technological parameters of processing, allowing efficient implementing the methods of electrochemical and electrolytic-plasma polishing. The experimental data obtained during processing additive parts, in particular, the profilograms of surface irregularities and roughness indicators, such as the roughness class and the arithmetic mean deviation of the irregularity profile, are analyzed. Proposals for the application of these processing methods in practice are put forward. Perspective directions for the development of the proposed methods for processing additive parts, primarily of complex shape, are considered.

Electrolytic plasma polishing of NiTi alloy

Nitinol is widely used in the production of medical devices, especially the ones that are designed for minimally invasive treatment, such as stents to restore vascular patency, stent grafts to eliminate aneurysms, and cava filters to trap blood clots. One of the most important characteristics that determines the reliability of the functioning of such products in the human body is the state of the surface layer. The higher the surface quality, the less negative impact is on the circulatory system, the walls of blood vessels and the higher the biological compatibility of the product. Electrochemical polishing methods are mainly used to improve the surface quality of nitinol products. The disadvantage of the applied electrochemical methods is the need to use aggressive electrolytes that contain toxic components, such as hydrofluoric acid, sulfuric acid, perchloric acid, nitric acid, methanol. As an alternative to the existing methods of electrochemical polishing, we have developed electrolytic-plasma polishing (EPP), a new highly efficient process for improving the surface quality of nitinol products. The most important advantage of the method over traditional electrochemical polishing is the use of aqueous salt solutions with a concentration of 4 % as electrolytes. Based on the results of the studies performed, the most rational EPP mode was established, the use of which during polishing of nitinol provides surface cleaning from scale, polishing with a decrease in the roughness parameter Ra by 0.344 µm and an increase in pitting potential by 33 %.

Effect of electrolytic plasma polishing on microstructural evolution and tensile properties of 316L stainless steel

Electrolytic plasma polishing (EPP) is an advanced technique for high-quality surface finishing of metal and alloy materials. Austenitic 316L stainless steel (SS) is extensively used in various industrial applications due to its excellent comprehensive performance. Therefore, it is widely studied to improve its properties by specific means and methods and expand its scope of application. In this paper, the influence of EPP generated dynamic composite energy on the microstructural evolution and tensile properties of machined 316L SS is investigated. A decrease in the surface roughness (from 0.103 μm to 0.046 μm), average grain size (from 5.65 μm to 5.21 μm), and low angle grain boundaries (LAGBs) are observed, along with an increase in geometrically necessary dislocation density in post EPP samples. Post EPP, grains are found to be predominantly oriented in 〈101〉. Schmid factor variation (from 0.475 to 0.45) shows a reduction in plastic deformability of the material. The yield strength and tensile strength of the material is increased by 8.98% and 4.32%, approximately, after EPP treatment. The dynamic composite energy produced during the EPP process may induce a cavitational effect, causing (i) rupture of the vapor-gaseous envelope, (ii) high-energy plasma bombardment, and (iii) development of annealing stress inside the material, resulting in microstructural evolution of 316L SS.

Effect of Electrolytic-Plasma Polishing on the Mechanical Properties of Austenitic–Martensitic VNS9-Sh TRIP Steel

The effect of electrolytic-plasma polishing (EPP) on the mechanical properies of austenitic–martensitic VNS9-Sh TRIP sheet steel is investigated. EPP is found to exert a little effect on the static mechanical properties of VNS9-Sh steel due to some peculiarities of the strain-induced martensite formation during static tension. EPP increases the fatigue strength of the steel by decreasing the defect-induced stress concentration in the surface layer.

Plasma additive layer manufacture smoothing (PALMS) technology – An industrial prototype machine development and a comparative study on both additive manufactured and conventional machined AISI 316 stainless steel

Additive Layer Manufacturing (ALM) of metals is rapidly changing the landscape of industrial manufacturing. Its deployment is however still hindered by extremely rough native surfaces, and drastic difficulties in efficiently applying conventional finishing methods. This paper presents the PALMS process, derived from electrolytic plasma polishing, as a solution to this problem. The viability of the process on a scale compatible with commercial use is demonstrated with a prototype industrial implementation. PALMS was applied on AISI 316 stainless steel pieces produced either by ALM or by conventional machining (CM.) Surface states, microstructures and other properties were compared pre- and post-PALMS. Significant improvements in surface state were observed after a 10 min treatment, with a 5-fold reduction in roughness. ALM surfaces were not affected negatively by PALMS in any way measured, and showed slight improvements in hardness and pore density. Two PVD coatings (TiN and WCC) were finally applied Post-PALMS, to test the compatibility of the process with further industrially relevant surface treatments. PALMS enables good coating adhesion on ALM pieces, with improved friction and wear properties compared to their CM counterparts.

Investigation of the ignition phase in electrolytic plasma polishing under different starting conditions

Electrolytic plasma polishing is a hybrid process in which the electrolytic process is an assisting process for a plasma region, which subsequently cleans and polishes the surface of a workpiece. The basic process takes place in an electrolyte bath, where very different starting conditions can be met. The extreme cases are the ignition in the bath, the ignition during a rapid immersion phase and the ignition in a slow immersion phase. Characteristic of these individual cases are the extreme changes of the tool impedance in connection with the electrolyte. The paper shows how the current-voltage characteristic can be measured, without adjustment problems between the process energy source (PES) and the connection impedance. The individual phases of the ignition phase are explained on the basis of a phenomenological model and the changes in the model (equivalent circuit diagram) of the process are taken into account. From these findings, the conditions can be derived to the PES and energy consumption in the ignition phase can be minimized. The basic objective is also to convert the ignition phase into a stable polishing phase and to have as few re-ignition phases as possible during the polishing period. In particular, the boundary conditions for the Bath-PeP are defined, which allow for a fast polishing of the surface, without deteriorating the mechanical properties of the surface or changing the geometry of the functional surface. In contrast to electrolytic polishing, no edge rounding occurs if a correspondingly short processing time is maintained.

Heat balance calculation specifics with considered roughness reduction for jet-grouting hydraulic puller working surfaces finished by electrolytic plasma polishing

Heat balance calculation specifics with considered roughness reduction for jet-grouting hydraulic puller working surfaces finished by electrolytic plasma polishing

Electrolytic-plasma polishing of cobalt-chromium alloys for medical products

In the manufacture of implants that are subject to increased cyclic loads, cobalt-chromium alloys with high hardness- and wear resistance have recently been widely used. Roughness of working surfaces is one of the most important characteristics of such products. The traditional processes of finishing the surface of cobalt-chromium alloy implants are based on mechanical and electrochemical methods. The disadvantages of mechanical methods are low productivity, susceptibility to the introduction of foreign particles, difficulties in processing of complex geometric shapes. For electrochemical technologies the treated materials are considered intractable, harmful electrolytes, consisting of solutions of acids, are used in the process of polishing. As an alternative to existing methods, it was proposed to use an environmentally safe method of electrolytic-plasma polishing, the main advantage of which is the use of aqueous solutions of salts with a concentration of 3–5 % as electrolytes. According to the results of the technological process, it has been established that at most electrolyte-plasma polishing modes of cobalt-chromium alloys for medical purposes, a relief in the form of a grid of protrusions occurs on the surface, the origin of which can be explained by the heterogeneity of the material structure that occurs at the stage of casting. Moreover, the height of the formed relief protrusions has a direct impact on the amount of surface roughness. As a result of studies, electrolyte-plasma polishing process modes were established, ensuring the formation of a smooth surface without the presence of embossed protrusions, smoothing the microrelief with the removal of scratches resulting from pre-grinding, achieving a low roughness value (Ra 0.057 micron) and a high reflection coefficient (0.7), which fully meets the requirements for the surface of the implants.