Papers by Keyword: Plasma Electrolytic Oxidation (PEO)

Abstract: Plasma electrolytic oxidation (PEO) method allows obtaining multifunctional ceramic-like coatings with unique properties. This article examines the relevant problem of the electrolyte effect on the chemical composition of PEO coating. The corrosion resistance of titanium alloy various PEO coatings in corrosive liquids has been studied: 1N sodium hydroxide solution, concentrated sulphuric acid (80%), 1N sulphuric acid solution, concentrated hydrochloric acid (30%), 1N hydrochloric acid solution. Comparative analysis of the VT-1 titanium alloy chemical resistance showed that the most resistant to the effects of corrosive substances were samples with PEO coating formed in a hydrophosphate electrolyte Na₂HPO₄.

Abstract: The main goal of present paper is to obtain porous coatings enriched in copper by Plasma Electrolytic Oxidation on titanium and niobium as well as on NiTi and Ti6Al4V alloys. Performed SEM and EDS studies confirmed the hypothesis that it is possible to create the porous surfaces with pores, which shapes and size are different. In order to show the copper enrichment inside the surface layers, the copper-to-phosphorus ratios were used. Based on these ratios it may be concluded that average value of Cu/P is maximal for NiTi alloy after oxidation in electrolyte containing 300 g of copper nitrate in 1 liter of phosphoric acid and equals 0.26. The minimum of Cu/P ratio equaling to 0.12 was recorded for pure titanium and pure niobium treated in electrolyte containing 300 g of Cu (NO₃)₂ in 1 L H₃PO₄.

Abstract: The electrochemical corrosion and mechanical properties of ceramic coatings fabricated by plasma electrolytic coating (PEO) and hard anodizing (HA) methods comparatively examined for AA2219. Potentiodynamic polarization results revealed that the corrosion resistance of both coatings are comparable to each other. However, the indentation and scratch testing indicated that the hardness and modulus of the PEO coating was significantly higher when compared to HA coating. The critical load (Lc2) causing adhesive failure of the PEO coating was much high (19N) when compared to HA coating (10N) showing better adhesive strength of the PEO coating.Key words: Plasma electrolytic oxidation (PEO), potentiodynamic polarization, nanoindentation, hard anodizing

Abstract: Ceramic oxide coatings were produced on pure titanium by plasma electrolytic oxidation in different electrolytes. The variation of coating thickness with applied voltages revealed coating almost kept a steady-state growth rate in electrolyte A and B, but not for electrolyte C. Numerous nodules occurred on the surface of the coatings at 200V in electrolyte A and B, and then nodules disappeared with the applied voltage increasing to 300V. There was no nodules occurred, and pore size was evidently different in electrolyte C. When the applied voltage was 300V, the coating formed in electrolyte C exhibited the highest corrosion potential and lowest corrosion current density in 3.5% NaCl aqueous solution.

Abstract: A plasma electrolytic oxidation (PEO) ceramic coating process was used to form ceramic MoS2/oxide coatings on aluminum. The tribological properties of the PEO-MoS2 coatings were evaluated by sliding wear tests under the dry and lubricate conditions at the room temperature. The test results showed that the solid lubrication MoS2 can be integrated into the coatings for friction reduction. The role of solid lubrication in reducing friction coefficient has been exhibited more significantly in the oil test condition than in the dry test condition.

Abstract: TiO2 and MoS2/TiO2 coatings were prepared using a Plasma Electrolytic Oxidation (PEO) process at a unipolar pulsed-DC mode. Both coatings, mainly comprised of anatase TiO2, exhibited a low coefficient of friction, C.O.F < 0.21 for the TiO2 coating and C.O.F < 0.16 for the MoS2/TiO2 coating, while the MoS2/TiO2 coating had a longer wear life than TiO2-coated and uncoated Ti alloy (Ti-6Al-4V). This result showed that the solid lubricant MoS2 may play a significant role in the tribological behavior and it can be applied to many high load-bearing systems in aerospace and automotive industries.

Abstract: Zirconia coating was produced on Al-Si alloys by plasma electrolytic oxidation (PEO). The alkaline electrolyte containing Zr(OH)₄ powders was used. The composition and structure of the coating were investigated by SEM and XRD. The results show that in the initial stages of oxidation the growth of coating belongs to the stage of anodic oxidation controlled by electrochemical polarization. The growth of coating is mainly outward growth and the growth rate is faster. With elongated treated time and increased thickness of the coating, the growth of coating is mainly ingrowth. In contrast with the stage of anodization, the growth rate of plasma electrolytic oxidation is slower than anodization. The coating consists of t-ZrO₂, m-ZrO₂, α-Al₂O₃ and γ-Al₂O₃.T-ZrO₂ is the main phase and distributes in outer layer of the coating, however, α-Al₂O₃ appears in inner layer of the coating. Many micro-particles appear on the coating surface with dimension of 1-2μm.. In the process of plasma electrolytic oxidation, Zr(OH)₄ powders move and deposit on the mouth of plasma discharge channel under the effect of electric field force, then it is transformed to ZrO₂ by the high temperature of plasma discharge.

Abstract: The paper reported the effect of zirconia incorporation on the oxide layer modification of the valve metal such as magnesium coated by plasma electrolytic oxidation (PEO). To incorporate zirconia particles into the oxide layer, PEO coatings were carried out under AC condition in electrolytes containing zirconia powder. After PEO coatings, structure observation revealed that a number of zirconia particles were distributed uniformly throughout the oxide layer while the size and distribution of pores remained unchanged as compared to the results coated by PEO without zirconia. It was found that fine zirconia particles incorporated into the oxide layers played an important role in enhancing the anti-corrosion properties of bare metal.

Abstract: In order to get a clear picture for describing the growth process of plasma electrolytic oxidation coatings under escalating voltage waveform, the composition, the concentration of the dissolved Mg2+ of PEO coatings formed at different reaction stages were investigated. The voltage-current characteristics during the PEO process were also discussed.

Abstract: The discharge characteristics of the potassium fluorozirconate electrolyte during plasma electrolytic oxidation process were investigated. Phosphoric acid was applied as additives. Ceramic films were prepared on magnesium alloy in electrolytes with different content additives under constant voltage. The effect of additives on the pH of the electrolyte and the dissolution of the substrate were investigated. It was found that the additives could influence the pH and dissolved magnesium ions effectively.