Effects Of Micro-arc Oxidation Research Articles

A surface and corrosion characterisation of micro arc oxidation treated friction stir welded ZM21 and ZE41 magnesium alloy: a comparison study

Magnesium alloys have gained attention as promising materials in industrial applications, for their high specific strength and low density. Magnesium alloys have desirable mechanical properties, but their poor corrosion resistance prevents their safe implementation. Alloys such as ZM21 and ZE41, possess unique properties that provide improved machinability and increased red-hot strength, respectively, while remaining prone to corrosion. To improve corrosion resistance, surface treatments and coating processes are employed. Comparing the corrosion characteristics of ZM21 and ZE41 is vital for aerospace and automotive applications, directly affecting component durability, reliability, and performance against corrosion. Magnesium alloys are frequently joined through friction stir welding (FSW), hence, similar importance is provided to studying the corrosion performance of welds, since FSW introduces microstructural changes that alter corrosion performance of welded joints. The paper discusses electrochemical corrosion mechanisms and analyzes the effect of Micro Arc Oxidation (MAO) coating on electrode potential, passivity, and electrical resistance of ZM21 and ZE41 plates welded through FSW. MAO treatments were performed on both base material and FSW joints. The corrosion performance of MAO-coated FSWed ZM21 and ZE41 alloys was compared through the Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarisation (PDP) tests. The PDP test revealed that MAO treatment enhanced the corrosion resistance of both base and FSWed ZM21 and ZE41 magnesium alloys. There was an improvement in potential polarization (Rp) values from 565 Ω cm2 to 11245 Ω cm2 for ZM21 and from 1184.4 Ω cm2 to 11435.69 Ω cm2 for ZE41 alloys. While exhibiting improvements in corrosion resistance, MAO-treated ZE41 performed better than MAO-treated ZM21. PDP results were verified through confirmatory EIS results. Therefore, MAO treatments are effective methods to improve the corrosion performance of Mg alloys. Evaluation of MAO coating performance on various FSW Mg alloys and studying their corrosion performance is crucial for engineering material selection.

Effect of micro-arc oxidation on antimicrobial properties and biocompatibility of biomedical Ti-xFe alloys

In this paper, Ti-xFe (x = 3,5,9 wt%) alloys were surface modified by micro-arc oxidation (MAO) to improve both antimicrobial properties and biocompatibility. The surface morphology, phase composition, and chemical composition of MAO treated Ti-xFe alloys were analyzed by XRD, XPS, SEM and EDS. The roughness, hydrophilicity, corrosion resistance, antimicrobial resistance and biocompatibility of Ti-xFe-MAO were tested by laser confocal microscopy, contact angle measurement, electrochemical tests, antimicrobial experiments and cellular assays to evaluate their potential as orthopedic implants materials. The roughness and hydrophilicity of Ti-xFe-MAO alloys were greatly enhanced with increasing the oxidation voltage. The Ti-xFe alloys micro-arc oxidized at 250 V and 300 V showed improved corrosion resistance and excellent antimicrobial and cytocompatibility properties. Hence, micro-arc oxidation should be an excellent surface modification to improve the biofunction of Ti-xFe alloy as an implant alloy.

Optimization of surface texture fabricated by three-step microarc oxidation for self-lubricating composite coating of diesel engine piston skirts

A surface texture produced by three-step microarc oxidation (MAO) was optimized to improve the tribology performance of a self-lubricating composite coating for diesel engine piston skirts. WS2 was introduced into the self-lubricating composite coating as a self-lubricating additive. The effects of MAO’s varying electrical parameters in terms of stages and action time on the microstructure and chemical composition of the coatings were analyzed by XPS mapping, micron CT, SEM, XRD, and EDS mapping. Furthermore, friction-wear tests under dry lubricating were employed to evaluate the self-lubricating property of the composite coating. Compared to the bare ZL109 aluminum alloy, the optimized composite coating’s friction coefficients were reduced by 60%. Notably, the wear loss of cylinder liner samples matched with the optimized composite coating was almost zero under this work condition.

Microstructure and Wear Properties of Micro Arc Oxidation Ceramic Coatings.

The interaction effect of micro arc oxidation (MAO) parameters on the microstructure and wear properties was investigated. The results showed that the electric current and oxidation time significantly influenced the thickness and grinding crack width of the ceramic coatings within the range of the selected parameters, and the interaction effect of the electrical parameters was not obvious. The surface morphology, cross-section morphology, and element distribution of the coatings were observed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that ceramic coatings with γ-Al2O3 and α-Al2O3 formed, which enhanced the coating performance. After that, the microhardness and wear resistance were tested. Under the optimal process, the microhardness of a coating section was up to 1200 HV0.1, and the friction coefficient was just 0.3. When wear occurred, the volcanic microstructures experienced extrusion and deformation, and then peeled off under shear stress, which led to the formation of a grinding crack. The main failure modes of the micro arc oxidation coatings were abrasive wear and spalling failure.

Effect of Micro-Arc Oxidation on Friction–Wear Behavior of Cold-Sprayed Al Coating in 3.5 wt.% NaCl Solution

A cold-sprayed Al coating on S355 steel was processed using micro-arc oxidation (MAO). The friction–wear behavior of the obtained coating in 3.5 wt.% NaCl solution was investigated using a wear test, and the effects of wear loads and speeds on the friction–wear performances of the MAO coating were analyzed. The results show that the MAO coating is primarily composed of Al2O3, with no other phases. The average coefficients of friction (COFs) of the MAO coating under the wear loads of 0.5, 1.0 and 1.5 N are 0.48, 0.62, and 0.76, respectively, and the corresponding wear rates are 4.20 × 10−5, 4.21 × 10−5 and 4.27 × 10−5 mm3 m−1 N−1, exhibiting the higher wear resistance. Under the wear load of 1.0 N, the average COFs of the MAO coating at the wear speeds of 5.0, 6.7 and 8.3 Hz are 0.32, 0.45 and 0.62, respectively; and the corresponding wear rates are 3.21 × 10−5, 3.49 × 10−5 and 4.21 × 10−5 mm3 m N−1, respectively, which increase with the increase in wear speeds. The wear mechanism of the MAO coating is fatigue wear and abrasive wear, and its wear resistance was better than the cold-sprayed Al coating.

A PROPOSAL FOR MODIFIED GALVANIC CORROSION MODEL: INVESTIGATING EFFECTS OF MICRO-ARC OXIDATION ON Al ALLOY

Corrosion is generally an undesirable phenomenon in most engineering applications. The effects of micro-arc oxidation (MAO) coating on Al alloy on the galvanic corrosion performance have been studied. The surface micro-structures were characterized using scanning electron microscope (SEM) and metallographic microscope before and after corrosion. Electrochemical studies on the corrosion behaviors have been reported by using open circuit potential (OCP) and potentiodynamic polarization (PDP) measurements in a slurry solution. All measurements were consistent with each other and showed that the MAO coating can significantly reduce the corrosion rate of Al alloy. A model for elucidating corrosion mechanism and corrosion process of the MAO coating on Al alloy is proposed.

Effect of micro arc oxidation on micro – structure and electrochemical corrosion performance of cold sprayed aluminum coating

PurposeTo improve the electrochemical corrosion resistance of cold sprayed Al coating.Design/methodology/approachA cold sprayed aluminum (Al) coating fabricated on S355 structural steel was oxidized using a micro arc oxidation (MAO). The electrochemical corrosion and impedance spectroscopy were tested to investigate its corrosion performance.FindingsThe MAO film is primarily α-Al2O3 and γ-Al2O3, which increases its density and surface quality. The corrosion potential is positively shifted by 0.2 V, and the electrochemical impedance is significantly increased.Originality/valueA cold sprayed Al coating on S355 steel was first oxidized using a MAO. The effects of MAO on the microstructure of Al coating were investigated to analyze its electrochemical corrosion behavior.

The Effect of Microarc Oxidation on the Structure and Hardness of Aluminum-Oxide Coatings Formed by Plasma Spraying on Titanium

Coatings formed by plasma spraying of electrocorundum on VT6 titanium alloy and subsequent microarc oxidation at different current densities were examined. The parameters of structure and hardness of metal-oxide layers were studied. The effect of current density on them was also found. During microarc oxidation, the open porosity (from 50.3 ± 4.5 to 10.3 ± 1.5%), the thickness (from 47.4 ± 3.3 to 30.2 ± 5.3 μm), and the average size of structural elements of presprayed coating were decreased, while its hardness was increased from 760 ± 486 to 875 ± 238 HV2. The magnitude of changes in the structure of the plasma coatings depended on the current density during modification. Microarc oxidation makes it possible to form structural elements in the form of pores and crystals with a size from 15 to 150 μm on the surface of sprayed aluminumoxide coatings.

Comparative study on effects of different coatings on biodegradable and wear properties of Mg-2Zn-1Gd-0.5Zr alloy

Coating is one of the effective methods to improve the corrosion resistance of the biodegradable Mg alloys. In this work, comparative study on the effects of micro-arc oxidation (MAO) coating, SrP coating and CaP coating on the biodegradable and wear properties of Mg-2Zn-1Gd-0.5Zr alloy were investigated. The results showed that the degradation deposition contained Gd on the surfaces of both MAO coating and SrP coating, which stabilized the coating, thereby increasing the degradation resistance of the alloy. The wear test showed that MAO coating and CaP coating exhibited good wear resistance. For a 5 N loading, the sliding distances of MAO coating, SrP coating and CaP coating were 2.24 m, 0.29 m and 9.00 m respectively, before the coatings were completely destroyed. This investigation revealed that the MAO coating exhibits the best degradation resistance and the CaP coating exhibits the best wear resistance.

Surface Properties of TiNi Alloy Treated by Micro-Arc Oxidation under Different Voltages

The effects of micro-arc oxidation (MAO) voltage (370V, 400V, 420V) on the surface morphology, adhesion of film/substrate, corrosion resistance and fretting friction and wear properties after micro-arc oxidation and heat-treatment for 48h of TiNi alloy were investigated. The results show that, as the voltage gradually increases: (1) micro-arc oxidation coatings form, when the voltage increase to 420V, the coating shows a significant micro-arc oxidized porous characteristics; (2) the Ca/P ratio in the coatings also increases, so the Ca/P ratio can be controlled by adjusting the voltage of micro-arc oxidation; (3) the corrosion resistance of MAO coatings can be significantly improved by increasing the output voltage, the corrosion rate and the corrosion potential of 420V are smaller two magnitude than 370V’s; (4) the coating of 420V shows lower friction coefficient with higher resistance, narrower wear scar width; (5) the MAO coatings have formed different types of hydroxyapatite crystals (HA) after immersed in high temperature and pressure reactor for 48h, and the phase composition of the coating are mainly apatite.

The effects of micro arc oxidation of gamma titanium aluminide surfaces on osteoblast adhesion and differentiation

The adhesion and proliferation of human fetal osteoblasts, hFOB 1.19, on micro arc oxidized (MAO) gamma titanium aluminide (γTiAl) surfaces were examined in vitro. Cells were seeded on MAO treated γTiAl disks and incubated for 3 days at 33.5 °C and subsequently for 7 days at 39.5 °C. Samples were then analyzed by scanning electron microscopy (SEM) and alkaline phosphatase assay (ALP) to evaluate cell adhesion and differentiation, respectively. Similar Ti-6Al-4V alloy samples were used for comparison. Untreated γTiAl and Ti-6Al-4V disks to study the effect of micro arc oxidation and glass coverslips as cell growth controls were also incubated concurrently. The ALP Assay results, at 10 days post seeding, showed significant differences in cell differentiation, with P values <0.05 between MAO γTiAl and MAO Ti-6Al-4V with respect to the corresponding untreated alloys. While SEM images showed that hFOB 1.19 cells adhered and proliferated on all MAO and untreated surfaces, as well as on glass coverslips at 10 days post seeding, cell differentiation, determined by the ALP assay, was significantly higher for the MAO alloys.

Effects of different treatments on the bond strength of titanium to porcelain

This study focused on the effects of micro-arc oxidation on the bond strength of the porcelain-titanium system. The phase, morphology, and oxide layer thickness of titanium were evaluated. In particular, the bond strength of porcelain fused to titanium was measured using a three-point bending test. Statistical analyses were performed using a one-way analysis of variance. Differences in the surface morphologies and the phase components were observed in three groups. For micro-arc oxidation specimens, the bonding of titanium and porcelain was compact with a thin oxide layer. The mean bond strength of the micro-arc oxidation group, pre-oxidation group and control group was 42.40 ± 4.35 Mpa, 34.28 ± 2.84 Mpa, and 28.58 ± 2.74 Mpa, respectively. When titanium was subjected to micro-arc oxidation treatment, the bond strength was significantly increased compared with the pre-oxidation group and the control group (p < 0.05). These results suggest that the micro-arc oxidation treatment could be an effective but simple method for increasing the titanium-ceramic bonding strength.

Biodegradable Behaviors in Simulated Body Fluid of Mg-Gd-Y-Zr Alloy with Micro-Arc Oxide Coating

The effects of micro-arc oxidation (MAO) on corrosion resistance of Mg-Gd-Y-Zr magnesium alloy have been studied. The Mg-Gd-Y-Zr with thicker oxide coating presented higher corrosion resistance in simulated body fluid (SBF). The corrosion rates were measured by several methods including hydrogen evolution volume measurement, weight-loss method and determination of pH as an auxiliary reference. The surfaces of specimens were observed by SEM and white light confocal microscopy before and after the corrosion. Besides the effects of MAO, the pitting resulted from breakage of oxide coating played a notable role as well. This provided a new direction towards the enhancement of corrosion resistance of magnesium alloy.

Effects of micro-arc oxidation coating on corrosion behavior of Mg-Y-Zn in simulated body fluid

The application of magnesium and its alloy as degradable biomaterials is mainly confined due to its high degradation rate in physiological environment. This research focused on the effects of micro-arc oxidation (MAO) on biodegradable behavior of Mg-Y-Zn magnesium alloy in a simulated body fluid (SBF). The corrosion rate of alloys was gauged by means of hydrogen evolution volume measurement and mass-loss method. Scanning electron microscope (SEM) was utilized to observe the surface of the magnesium alloy and the cross-section of oxidation coating layer before and after corrosion. The Mg-Y-Zn alloy with thicker oxidation coating exhibited greater corrosion resistance during the immersion test for 240 h.

Effect of microarc oxidation on the corrosion and mechanical behavior of cast aluminum alloys

Effect of microarc oxidation on the corrosion and mechanical behavior of cast aluminum alloys