Plasma Electrolytic Oxidation Research Articles

Enhanced Surface Properties of TiO2-Based Coatings via Stevia-Assisted Spark Suppression: Insights from Density Functional Theory Calculations

This study investigates the enhancement of surface properties in TiO2-based coatings on the Ti-6Al-4V alloy through micro-arc oxidation (MAO), employing stevia sugar as a novel additive. By incorporating stevia sugar into acetate–glycerophosphate–tetraethoxysilane solutions used in MAO treatment, the porous morphology of TiO2-based oxide layers is regulated. The incorporation of stevia moderates plasma discharge intensity, facilitating the formation of a uniform silicon-rich structure characterized by reduced porosity and pore size. This effect is attributed to the interaction between stevia and tetraethyl orthosilicate (TEOS), which modifies the TEOS hydrolysis process, thereby enhancing structural uniformity and stability while concurrently reducing plasma discharge intensity. Additionally, theoretical calculations offer a valuable understanding of the reactivity and interactions of stevia, TEOS, and their complex during the MAO process, laying the groundwork for further research and optimization in this promising field.

Effects of nano-SiO2 particle addition on the structure and properties of micro-arc oxidation ceramic coatings on 7075 aluminum alloy

Purpose The purpose of this study is to investigate the influence of varying concentrations of nano-SiO2 particle doping on the structure and properties of the micro-arc oxidation (MAO) coating of 7075 aluminum alloy. This research aims to provide novel insights and methodologies for the surface treatment and protection of 7075 aluminum alloy. Design/methodology/approach The surface morphology of the MAO coating was characterized using scanning electron microscope. Energy spectrometer was used to characterize the elemental content and distribution on the surface and cross section of the MAO coating. The phase composition of the MAO coating was characterized using X-ray diffractometer. The corrosion resistance of the MAO coating was characterized using an electrochemical workstation. Findings The results showed that when the addition of nano-SiO2 particles is 3 g/L, the corrosion resistance is optimal. Originality/value This study investigated the influence of different concentrations of nano-SiO2 particles on the structure and properties of the MAO coating of 7075 aluminum alloy.

Microstructure and properties of a MAO/PA/MoS2 composite coating formed on 6063 aluminum alloy by micro arc oxidation

Different self-sealing and lubricating composite coatings were produced on 6063 Al alloy using micro arc oxidation (MAO) with MoS2 and/or phytic acid (PA) incorporated into the base electrolyte. The tribological properties and electrochemical corrosion behavior of the coatings were detailed investigated in this paper. The results showed that the coefficient of frictional (CoF) of MAO/MoS2 coating decreased 29.6 % compared to that of the pure MAO coating due to the excellent self-lubricating of MoS2. Meanwhile, the CoF of MAO/PA/MoS2 coating reduced 39.5 % attributed to a thicker and more compact coating obtained by the addition of PA as an intermediate chelating agent besides the self-lubricating effect of MoS2 particles. The pores were sealed by MoS2 during MAO process due to the electrodeposition effect which resulted in a positive shifting of the corrosion potential. However, the improvement of corrosion resistance for the MAO/MoS2 coating was limited as the intrinsic defects in MoS2 lattice preferred to form micro galvanic cell. The corrosion current density of the MAO/PA/MoS2 coating was three orders of magnitude lower than that of pure MAO coating. The thin PA layer produced at the substrate/coating interface of the MAO/PA/MoS2 coating can act as a barrier to suppress the galvanic corrosion, inducing the best corrosion resistance of the coating.

Tribological properties of MAO ceramic coatings with annulus array texture on disposable surgical gloves

Introduction: In recent research, the expansion in the use of Mg alloys for biomedical applications has been approached by modifying their surfaces in conjunction with micro-arc oxidation (MAO) techniques which enhance their abrasion and corrosion resistance.Methods: In this study, combining laser texturing and MAO techniques to produce the dense ceramic coatings with microstructures. On the surface of the AZ31 Mg alloy, a micro-raised annulus array texture has been designed in order to increase the surface friction under liquid lubrication and to improve the operator’s grip when holding the tool. For this work, the micro-morphology of the coatings was characterised, and the friction properties of the commonly used scalpel shank material 316 L, the untextured surface and the textured surface were comparatively analysed against disposable surgical gloves.Results and discussion: The results show that the Laser-MAO ceramic coating grows homogenous, the porosity decreases from 14.3% to 7.8%, and the morphology after friction indicates that the coating has good wear resistance. More specifically, the average coefficient of friction (COF) of the three types of gloves coated with Laser-MAO ceramic was higher than that of the 316 L and MAO ceramic coatings under the action of the annulus-integrated texture under the lubrication conditions of physiological saline and defatted sheep blood, which achieved the goal of increasing friction for the purpose of helping to prevent the problem of tool slippage from the hand.

Effect of electrical modes on dielectric and insulation properties of plasma electrolytic oxidation ceramic films on Al

Effect of electrical modes on dielectric and insulation properties of plasma electrolytic oxidation ceramic films on Al

Preparation and properties of micro-arc oxidation ceramic coatings using machine vision technology

Preparation and properties of micro-arc oxidation ceramic coatings using machine vision technology

Superior MoTiN and NiMoTiN coating electrode with platinum-like catalytic activity fabricated by plasma electrolytic oxidation

Electrolyzing water is an effective and feasible technology to achieve a large-scale hydrogen production in industry. However, it is still challenging to develop an efficient approach to fabricate a superior and stable hydrogen evolution reaction (HER) electrodes with low cost and outstanding catalytic efficiency. This work presents an innovative surface modification technique of plasma electrolytic oxidation (PEO) to fabricate superior MoN based coating electrodes. By simply introducing Na2MoO4 and NiAc2 into the electrolyte, a novel MoTiN and NiMoTiN coatings were successfully achieved on the surface of a titanium substrate by PEO and annealing treatments, which exhibits excellent mechanical adhesion and platinum-like catalytic properties. Importantly, it has been demonstrated that the newly formed MoTiN solid solution combined by active Mo2N and conductive TiN can contribute the superior catalytic activity and the subsequent Ni doping can effectively stabilize the structure and activity of MoTiN. Under the alkaline environment of 1 M KOH, the MoTiN and NiMoTiN coated electrodes require only 126 and 121 mV overpotential, respectively, to achieve a current density of 10 mA cm−2. Additionally, under the same test conditions, NiMoTiN can operate stably for over 24 h, demonstrating excellent HER catalytic activity and stability. This work provides new insights into the preparation of HER electrodes with superior mechanical properties and excellent catalytic performance towards industrial hydrogen production.

Experimental Design of the Adhesion between a PEI/Glass Fiber Composite and the AA1100 Aluminum Alloy with Oxide Coating Produced via Plasma Electrolytic Oxidation (PEO)

In this study, the AA1100 aluminum alloy underwent the plasma electrolytic oxidation (PEO) process to enhance its adhesion to a thermoplastic composite of polyetherimide (PEI) reinforced with glass fiber, following ASTM D1002:10 standards. A 23 factorial design was employed, varying three parameters in the oxidation process: immersion time, applied electric potential, and electrolyte concentration (Na2B4O7). The joining of aluminum and thermoplastic composite samples was achieved through oxy-fuel welding (OFW), using oxygen and acetylene gases. For the characterization of the joined samples, a universal tensile testing machine was utilized with a displacement speed of 1.5 mm/min. The analysis of the oxide coating involved scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR). Through variance analysis, it was determined that the statistical model encompasses approximately 80% of the variability in the adhesion process between materials. An improvement of up to 104% in adhesion between the materials was observed with the process, indicating an effective bond due to the presence of the thermoplastic matrix in the treated aluminum sample. This improvement is attributed to the morphology of the oxide coating, resembling corals, with micro-pores and recesses that facilitated mechanical anchoring.

Improved bioactivity and corrosion resistance of NbO containing plasma electrolytic oxidation coating on ZM21 Mg alloy

ABSTRACT The present study reports the effect of niobium oxide (NbO) phase on the microstructure, corrosion, and bioactivity of coating on ZM21 Mg alloy by plasma electrolytic oxidation (PEO) process. NbO containing coatings are obtained by adding Potassium Niobate (KNbO3) along with the base electrolyte system, while the base electrolyte system consisted of sodium phosphate (Na3PO4⋅12 H2O) and potassium hydroxide (KOH). X-Ray Diffraction (XRD) was used for phase analysis, and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) was employed to extract the microstructural features. Tafel curves were generated to study the corrosion behaviour, and bioactivity test was conducted in the simulated body fluid (SBF) for 14 days to study the bioactivity. XRD results revealed that the PEO coatings consisted of MgO phase, whereas the sample coated in the electrolyte containing KNbO3 showed NbO phase in addition to MgO phase. NbO containing coating showed higher corrosion resistance and excellent bioactivity.

Effect of NdCl3 on characteristics of micro-arc oxidation coating formed on TC4 alloy

Effect of NdCl3 on characteristics of micro-arc oxidation coating formed on TC4 alloy

STUDY OF THE INFLUENCE OF PLASMA-ELECTROLYTICE OXIDATION PARAMETERS ON THE FUNCTIONAL PROPERTIES OF HETEROXIDE COATINGS

The results of a study of the influence of the parameters of plasma-electrolytic oxidation in diphosphate electrolyte solutions of metal platforms made of titanium alloys, as the basis for the formation of heterooxide coatings with photocatalytic activity, on the level of their functional properties are presented. It has been established that heterooxide coatings obtained in PEO modes on titanium alloy platforms, in which zinc and tungsten compounds were incorporated as dopants, demonstrate photocatalytic activity in the processes of azo dye degradation under UV irradiation. An increase in the concentration of oxygen-containing compounds of dopants in electrolyte solutions has a positive effect on their incorporation into the composition of the monoxide matrix of the composite, morphology and catalytic properties of the obtained coatings. Based on the results of determining the morphological features of the structure of the coatings, it was proved that, compared with titanium monoxide, as a material for a photocatalytic platform, heterooxide coatings have a more developed globular surface microstructure, which positively affects the level of their functional performance. A symbatic dependence between the content of incorporated dopants and the specific surface area of coatings, as well as their photocatalytic activity, has been proven. It is noted that the change in the phase structure of the surface layers in the process of plasma-electrolytic formation of the TiO/ZnO-WO3 coating on the surface of the carrier metal causes an increase in the mechanical characteristics of the resulting coatings, in particular, the microhardness almost doubles. The obtained results can become the basis for the creation of functional materials for the catalytic neutralization of natural, synthetic and man-made toxicants, which will lead to the solution of a number of environmental problems both during the war crisis and during the post-war reconstruction of the country.

The influence of rolling on the corrosion and wear resistance of the MAO coating on ZM5 alloy

Purpose The impact of rolling on the performance of micro arc oxidation (MAO) coatings on ZM5 alloy has been underreported. The purpose of this study is to explore the correlation between rolling and the failure mechanism of MAO coatings in greater depth. Design/methodology/approach The influence of rolling on the corrosion and wear properties of MAO coating was investigated by phase structure, bond strength test (initial bond strength and wet adhesion), electrochemical impedance spectroscopy and wear test. The change of the surface electrochemical properties was studied by first principles analysis. Findings The results showed that the MAO coating on rolled alloy had better corrosion and wear resistance compared to cast alloy, although the structure and component content of two kinds of MAO coating are nearly identical. The difference in interface bonding between MAO coating and Mg substrate is the primary factor contributing to the disparity in performance between the two types of samples. Finally, the impact of the rolling process on MAO coating properties is explained through first-principle calculation. Originality/value A comprehensive explanation of the impact of the rolling process on MAO coating properties will provide substantial support for enhancing the application of Mg alloy anticorrosion. Graphical abstract

Lithium-Doped Titanium Dioxide-Based Multilayer Hierarchical Structure for Accelerating Nerve-Induced Bone Regeneration.

Despite considerable advances in artificial bone tissues, the absence of neural network reconstruction in their design often leads to delayed or ineffective bone healing. Hence, we propose a multilayer hierarchical lithium (Li)-doped titanium dioxide structure, constructed through microarc oxidation combined with alkaline heat treatment. This structure can induce the sustained release of Li ions, mimicking the environment of neurogenic osteogenesis characterized by high brain-derived neurotrophic factor (BDNF) expression. During in vitro experiments, the structure enhanced the differentiation of Schwann cells (SCs) and the growth of human umbilical vein endothelial cells (HUVECs) and mouse embryo osteoblast progenitor cells (MC3T3-E1). Additionally, in a coculture system, the SC-conditioned media markedly increased alkaline phosphatase expression and the formation of calcium nodules, demonstrating the excellent potential of the material for nerve-induced bone regeneration. In an in vivo experiment based on a rat distal femoral lesion model, the structure substantially enhanced bone healing by increasing the density of the neural network in the tissue around the implant. In conclusion, this study elucidates the neuromodulatory pathways involved in bone regeneration, providing a promising method for addressing bone deformities.

Large amplitude voltage oscillations during plasma electrolytic oxidation (PEO) of niobium and their correlation with the porous morphology

Plasma electrolytic oxidation (PEO) is a technique that has been widely studied to obtain thick anodic oxide coatings based on aluminum, titanium, niobium, and other valve metals. In the case of niobium oxides, they are attractive because of their properties as semiconductors, biocompatibility, and high corrosion resistance. The electrochemical behavior during this process can vary according to the PEO parameters and influence characteristics such as coating thickness, adherence, morphology, and crystalline structure of the oxide film. In this study, unusual voltage oscillation transients are observed during the anodization of niobium under a galvanostatic PEO regime. The niobium substrates were anodized in three different electrolytic solutions (H3PO4, KOH, and C2H2O4), and the influence of temperature on the oscillation aspects in each one was investigated. In addition, three different current densities were tested to check the effect of this parameter on voltage oscillations. Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), and X-ray Diffraction (XRD) are used to characterize the samples. The results indicate a relationship between the exposed surface area and the pore morphology during the film growth in the oscillatory regime. A simultaneous process of oxide dissolution/pore filling and the micro-discharges observed during the PEO process is proposed.

Tribological properties of aluminum alloy coated with graphene oxide/polyvinyl alcohol composites after micro-arc oxidation

Purpose Aluminum alloy is considered an ideal material in aerospace, automobile and other fields because of its lightweight, high specific strength and easy processing. However, low hardness and strength of the surface of aluminum alloys are the main factors that limit their applications. The purpose of this study is to obtain a composite coating with high hardness and lubricating properties by applying GO–PVA over MAO coating. Design/methodology/approach A pulsed bipolar power supply was used as power supply to prepare the micro-arc oxidation (MAO) coating on 6061 aluminum sample. Then a graphene oxide-polyvinyl alcohol (GO–PVA) composite coating was prepared on MAO coating for subsequent experiments. Samples were characterized by Fourier infrared spectroscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The friction test is carried out by the relative movement of the copper ball and the aluminum disk on the friction tester. Findings Results showed that the friction coefficient of MAO samples was reduced by 80% after treated with GO–PVA composite film. Originality/value This research has made a certain contribution to the surface hardness and tribological issues involved in the lightweight design of aluminum alloys. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0427/

High-performance ceramic coatings for additive manufacturing biofunctional titanium alloy by regulating precipitation orientation

To prepare high-performance plasma electrolytic oxidation (PEO) coatings with excellent wear resistance and antibacterial activity on biofunctional alloys, Ti-Cu alloy was fabricated by additive manufacturing (AM) technique with controlled crystalline orientation of precipitates to enhance Cu ions release during PEO. In contrast to ingot metallurgical (IM) Ti-Cu alloy with Ti2Cu-(103)-oriented, the Ti2Cu-(110)-oriented in AM-Ti-Cu alloy exhibits a lower work function and inferior corrosion resistance due to its low atomic close-packing. This facilitates the release of Cu ions by promoting valence electron escape from the 4 s energy level during PEO to promote forming a higher content copper oxide (CuO). Subsequent to the PEO treatment, the AM-PEO coating contains more CuO (44.44 wt%) compared to the IM-PEO coating (3.6 wt%), resulting in better corrosion resistance and a lower friction coefficient (0.13 for AM-PEO and 0.34 for IM-PEO). The antibacterial efficacy of AM-PEO coating reached 99.62 %. This study highlights the advantage of regulating precipitate phase orientation in AM processes as an innovative approach to efficiently fabricate functional PEO coatings for alloys.

High-temperature degradation behavior of PEO-coated ZIRLO alloy in N2 and N2+steam environments at 900 and 1000 °C

A compact oxide coating of ∼10 μm thick on ZIRLO alloy was fabricated by plasma electrolytic oxidation (PEO). The morphologies, compositions, phase constituents before and after exposures in N2 and N2+steam environments at 900 and 1000 °C were characterized. The PEO coating greatly enhanced the corrosion resistance of ZIRLO alloy in the N2+steam atmosphere at 900 and 1000 °C. The kinetic curves transformed from parabolic behavior for bare alloy and exponential behavior for PEO-coated alloy at pre-transition stage to linear at post-transition stage, due to the formation of ZrN and its re-oxidation.

Improving the Wear Resistance Properties of 7A04 Aluminum Alloy with Three Surface Modification Coatings

Multiple advantages, such as good formability, high specific strength, excellent thermal conductivity, and high corrosion resistance, enable aluminum alloy wide application in various fields; however, low surface hardness and poor wear resistance limit its further development. In this study, three surface modification coatings were successfully prepared on the surface of 7A04 aluminum alloy by microarc oxidation (MAO) and a combination of hard anodizing treatment (HA) and physical vapor deposition (PVD), named MAO, HA+W+DLC, and HA+Ti+ta-C, respectively. The microstructure, hardness, and tribological properties of the three coatings and the 7A04 aluminum alloy substrate were studied. The results show that the surface quality and hardness of the coated samples were higher than those of the 7A04 aluminum alloy and that the HA+Ti+ta-C coating possessed the highest hardness of 34.23 GPa. Moreover, the wear resistance of the two multilayer coatings was significantly improved during the ring-block wear tests under oil lubrication, exhibiting a wear rate of 1.51 × 10−7 mm3/N·m for HA+W+DLC and 1.36 × 10−7 mm3/N·m for HA+Ti+ta-C.

The Tribological Properties of Plasma Electrolytic Oxidation Layers Synthesized on Arc Spray Coatings on Aluminum Alloys in Contact with Various Friction Materials

Oxide layers on the surface of the aluminum alloys D16 and AMg6 and on arc coatings sprayed with electrode wires made of the alloys D16 and AMg6 were synthesized using plasma electrolytic oxidation (PEO). The microstructure, phase composition and micro-hardness of the PEO layers were studied. In addition to the two main phases (α-Al2O3 and γ-Al2O3), a small amount of a metastable crystalized Al2.427O3.64 phase was found in their structure. A comparison was made of the wear resistance and friction coefficients of the synthesized PEO layers during friction tests in pairs with other PEO layers, a galvanic chromium coating, cast iron, steels and bronze of the BrC30 type. The results of the friction tests for the various PEO layers on aluminum alloys in tribo-contact with high-hardness elements made of hardened or chrome-plated steel justify the possibility of their use in a friction pair. We experimentally showed the influence of glycerin additive in motor oil 15W30 on the change in the friction coefficient of the PEO layers synthesized on the aluminum alloys and on the arc-sprayed coatings on their surfaces in tribocouples with hardened steel.

A Review of Corrosion-Resistant PEO Coating on Mg Alloy

The corrosion problem of Mg alloy limits its application in many engineering fields. Plasma electrolytic oxidation (PEO) is an economical and eco-friendly technology that can create a dense oxide layer on Mg alloy, offering a solution to the corrosion issue. This research summarizes the use of PEO technology in developing corrosion-resistant coatings for Mg alloys and examines the growth mode and corrosion process of PEO coatings. It is concluded that current efforts to enhance the corrosion resistance of PEO coatings on Mg alloys can be categorized into two approaches: improving the internal structure of the coating and enhancing the phase composition. This includes optimizing coating thickness, roughness, and density; repairing micropores and cracks; and introducing corrosion-resistant compounds by doping. Micropores and cracks are identified as vulnerable points for corrosion, and sealing is an effective strategy to address this. By modifying the phase composition of the coating, corrosion occurrence can be minimized, significantly boosting the corrosion resistance of Mg alloys. Finally, future challenges and potential advancements in corrosion-resistant PEO coatings for Mg alloys are discussed.