Research on Properties and Formation Mechanism of Ceramic Coatings Prepared by Micro-Arc Oxidation on 2024 Aluminum Alloy Surface

2006 ◽  
Vol 315-316 ◽  
pp. 259-263 ◽  
Author(s):  
Wan Sheng Zhao ◽  
T.Z. Xin ◽  
Zhen Long Wang ◽  
J.C. Liu
Keyword(s):  
Phase Composition ◽  
Ceramic Coatings ◽  
High Energy ◽  
High Energy Density ◽  
Alloy Surface ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
2024 Aluminum Alloy ◽  
Micro Arc Oxidation ◽  
Coating Formation

In this paper, ceramic coatings prepared on 2024 Al alloy surface in electrolyte by micro-arc oxidation are studied. The parameter of discharge and rate of ceramic coating formation are investigated. We analyzed microstructure and phase composition of the coatings by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), and studied the tribological performance of the coatings. The reactions on the electrode surface are deduced and the mechanism of coating formation has been analyzed. The results show that the relation between the thickness and reaction time is not linear. The ceramic coatings contain phase γ-Al2O3 andα-Al2O3; there is a big difference in contents of phase composition between inner coating and outer coating due to the different cooling rates of them. In MAO process, the coating undergoes a course of melting, solidifying and cooling. The coating can be divided into three layers, namely, transition layer, compact layer, and loose layer. The coating and substrate adheres firmly by a metallurgical process. Not only the elements of electrolyte (K, Si) and substrate (Cu) are found in the coatings but also the element of cathode (Fe). The Si-Al-O complex compound is formed in the discharge channels under high energy density condition.

EFFECTS OF α-Al2O3 NANOADDITIVE ON THE PROPERTIES OF CERAMIC COATINGS PREPARED IN BORATE ELECTROLYTE BY MICRO-ARC OXIDATION

2012 ◽  
Vol 19 (04) ◽  
pp. 1250038 ◽  
Author(s):  
H. X. LI ◽  
H. H. ZHU ◽  
X. WU ◽  
Z. G. JI
Keyword(s):  
Phase Composition ◽  
Great Influence ◽  
Ceramic Coatings ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
Micro Arc Oxidation ◽  
Edx Analyses ◽  
6063 Aluminum Alloy ◽  
Α Al2o3 ◽  
Wear Tests

Ceramic coatings have been synthesized on 6063 aluminum alloy by micro-arc oxidation (MAO) technique in the solution of Na2B4O7 electrolyte with and without α- Al2O3 nanoadditive. Effects of α- Al2O3 nanoadditive on the phase composition, micro-structure, micro-hardness, adhesion and wear resistance of the prepared ceramic coatings have been investigated in this paper. The phase composition and microstructure of the MAO coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX) analyses, respectively. Micro-hardness, adhesion and tribological and wear tests were also performed. The results showed that the α- Al2O3 nanoadditive doped in the electrolyte had great influence on the structural and mechanical properties of the ceramic coatings.

scholarly journals Influence of silicon on growth mechanism of micro-arc oxidation coating on cast Al–Si alloy

2018 ◽  
Vol 5 (7) ◽  
pp. 172428 ◽  
Author(s):  
Huijun Yu ◽  
Qing Dong ◽  
Yang Chen ◽  
Chuanzhong Chen
Keyword(s):  
Surface Morphology ◽  
Adhesive Strength ◽  
Growth Process ◽  
Substrate Surface ◽  
Ceramic Coatings ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Alloy Substrate ◽  
Micro Arc Oxidation

Micro-arc oxidation (MAO) is a plasma-assisted electrochemistry method to prepare protective ceramic coatings on aluminium alloys. Alloy elements of the Al-alloy substrate, such as Si, Cu, Mg and Li, have effects on the microstructure and composition of the MAO coatings. Usually, silicon distributes in the cast Al–Si alloy substrate as small laths and they cover approximately 10% of the substrate surface. Therefore, their effects on the growth process and microstructure of the MAO coatings are worthy of notice. In the present study, oxide coatings with a thickness of 15–18 µm were prepared on the ZL109 Al–Si alloy by MAO. The phase content, surface morphology and element distribution of the coatings were investigated by X-ray diffraction, grazing incidence X-ray diffraction, scanning electron microscope, and electron probe micro-analysis respectively. The average hardness of the coatings was 622.3 ± 10.2 HV 0.05 . The adhesive strength of the coatings is 40.55 ± 2.55 N, and the adhesion of the coatings could be rated as 5B by tape test according to ASTM D3359-17 standard test methods, which indicated a high adhesive strength between the MAO coating and substrate. The effects of silicon laths on surface morphology and composition of the coatings were discussed, and a model was put forward to describe the growth process of the MAO coatings on cast Al–Si alloys. The authors believe that the high silicon content of the substrate has no adverse influence on the structure and properties of the MAO coating on the ZL109 alloy.

Phase composition depth profiles using spatially resolved energy dispersive X-ray diffraction

2004 ◽  
Vol 37 (6) ◽  
pp. 967-976 ◽  
Author(s):  
Andrew C. Jupe ◽  
Stuart R. Stock ◽  
Peter L. Lee ◽  
Nikhila N. Naik ◽  
Kimberly E. Kurtis ◽  
...  
Keyword(s):  
Phase Composition ◽  
Spatial Resolution ◽  
Zinc Coating ◽  
High Energy ◽  
Sulfate Attack ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spatially Resolved ◽  
Composition Profiles

Spatially resolved energy dispersive X-ray diffraction, using high-energy synchrotron radiation (∼35–80 keV), was used nondestructively to obtain phase composition profiles along the radii of cylindrical cement paste samples to characterize the progress of the chemical changes associated with sulfate attack on the cement. Phase distributions were acquired to depths of ∼4 mm below the specimen surface with sufficient spatial resolution to discern features less than 200 µm thick. The experimental and data analysis methods employed to obtain quantitative composition profiles are described. The spatial resolution that could be achieved is illustrated using data obtained from copper cylinders with a thin zinc coating. The measurements demonstrate that this approach is useful for nondestructively visualizing the sometimes complex transformations that take place during sulfate attack on cement-based materials. These transformations can be spatially related to microstructure as seen by computed microtomography.

scholarly journals Phase composition of coatings on the D16 alloy during micro-arc oxdation in alkaline and silicate electrolytes

2020 ◽  
Vol 1,2020 (1,2020 (124)) ◽  
pp. 51-55
Author(s):  
Subbotina V ◽  
Belozerov V ◽  
Sobol’ O
Keyword(s):  
Phase Composition ◽  
Liquid Glass ◽  
Amorphous State ◽  
Practical Significance ◽  
Alkaline Electrolyte ◽  
X Ray ◽  
Micro Arc Oxidation ◽  
Coating Formation ◽  
Al2o3 Phase ◽  
Α Al2o3

Goal. The influence of electrolysis conditions at different electrolyte compositions on the phase formation of coatings obtained by micro-arc oxidation (MDO) on an aluminum alloy D16 was studied. Method. For electrolysis, two types of electrolytes were used: alkaline electrolyte (solution (KOH) in distilled water), silicate electrolyte (with different percentages of Na2SiO3 component). Research results. It was found that the phase composition of the MAO coatings obtained in an alkaline (KOH) electrolyte mainly consists of γ - Al2O3 phases and, to a much lesser extent, the α-Al2O3 phases. An increase in the KOH concentration leads to a shift in the γ – Al2O3 → α – Al2O3 polymorphic reaction toward the formation of the hardest α-Al2O3 phase (corundum). The formation of the preferred orientation of the growth of crystallites of γ – Al2O3 and α – Al2O3 phases during their formation in an alkaline electrolyte was not detected. Scientific novelty. A significant influence on the mechanism and processes of coating formation is made by the addition of liquid glass (Na2SiO3) in the electrolyte. In this case, the growth rate of the coating increases significantly, but the size of the ordering regions decreases from crystalline to X-ray amorphous. The phase composition of the MAO coatings, when they are formed in a silicate electrolyte, varies from a mixture of the γ - Al2O3 phase and mullite (3Al2O3 • 2SiO2) with a low content of liquid glass (10 g/l Na2SiO3) to the formation of only the X-ray amorphous phase with a high content of liquid glass in the electrolyte (50 g/l Na2SiO3). Practical significance. It was concluded that the use of an alkaline or silicate electrolyte with different percentages allows a wide variation of both the phase composition and structural state (α- Al2O3 and γ- Al2O3 phases, mullite (3Al2O3 • 2SiO2) or X-ray amorphous state) and the kinetics of growth the coating itself.

Structure and Property of Micro Arc Oxidation Ceramic Coatings on Al Alloy in K2ZrF6 Solution

2010 ◽  
Vol 105-106 ◽  
pp. 505-508 ◽  
Author(s):  
Zhen Dong Wu ◽  
Zhong Wen Yao ◽  
Fang Zhou Jia ◽  
Zhao Hua Jiang
Keyword(s):  
Wear Resistance ◽  
Corrosion Resistance ◽  
Aluminium Alloy ◽  
Friction And Wear ◽  
Ceramic Coatings ◽  
Al Alloy ◽  
Structure And Property ◽  
Micro Arc Oxidation ◽  
Disk Friction ◽  
Composition Structure

The coatings containing zirconia were produced on LY12 Aluminium alloy by micro-arc oxidation in K2ZrF6 and NaH2PO2 solution. The composition, structure, hardness, friction and wear resistance and corrosion resistance of the coating were studied by XRD, SEM, EDS, ball-on-disk friction tester and electrochemical analyzer, respectively. The results show that coating was composed of m-ZrO2 and t-ZrO2. There were a large amount of Zr and O and a little Al, P and K in the coating. The thickness of coating prepared for 3h was 168μm and the maximum value of the hardness was up to 16.75GPa. The friction and wear resistance and corrosion resistance were improved, compared with the LY12 aluminium alloy substrate.

Ceramic Coatings of Magnesium Alloy for Biomaterial Applications

2010 ◽  
Vol 434-435 ◽  
pp. 634-637 ◽  
Author(s):  
Pu Liang Zhang ◽  
Bin Liu ◽  
Dong Zhang ◽  
Yong Wei Tao ◽  
Sheng Rong Yang ◽  
...  
Keyword(s):  
Body Fluid ◽  
Ceramic Coatings ◽  
Alkaline Treatment ◽  
Mg Alloy ◽  
X Ray Diffraction ◽  
Electrodeposition Technique ◽  
Corrosion Properties ◽  
X Ray ◽  
Micro Arc Oxidation ◽  
Porous Oxide

Ceramic coatings were produced on magnesium (Mg) alloy of AZ91D for biomaterial applications by micro-arc oxidation (MAO) and electrodeposition methods. The morphology, microstructure, phase composition and corrosion properties of the prepared coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and potentiodynamic polarization tester, etc. The results indicated that a porous oxide layer was grown on the Mg alloy sheets after MAO process and the compositions of oxides were mainly Mg2SiO4 and MgO. After further electrodeposition and alkaline treatment, a flake-like structure diverging from centre to periphery was grown on the MAO coating and the coating was mainly made up of hydroxyapatite (HA). Moreover, the corrosion resistance of the Mg alloy after being treated with MAO and electrodeposition technique increases obviously, which was evaluated in stimulated body fluid (SBF).

Study On the Corrosion Resistance Properties of the Ceramic Coating Obtained Through Microarc Oxidation on the Aluminium Alloy Surface

2007 ◽  
Vol 353-358 ◽  
pp. 1733-1736 ◽  
Author(s):  
Fei Chen ◽  
Hai Zhou ◽  
Chen Chen ◽  
Fan Xiu Lu ◽  
Fan Xiu Lu
Keyword(s):  
Corrosion Resistance ◽  
Aluminium Alloy ◽  
Ceramic Coating ◽  
Microarc Oxidation ◽  
Electrochemical Corrosion ◽  
Nacl Solution ◽  
X Ray Diffraction ◽  
Micro Arc Oxidation ◽  
Coating Formation ◽  
Α Al2o3

Oxidation ceramic coating was directly synthesized on LY12 aluminium alloy by micro-arc oxidation (MAO) process in Na2SiO3 electrolyte solution with the Na2WO4-KOH-Na2EDTA addition. The corrosion resistance of the coating was tested using CS300P electrochemical corrosion workshop in 3.5% NaCl solution. Using the scanning electron microscopy (SEM) and X-ray diffraction (XRD), the cross-section microstructure, the surface morphology and the phase structure of the micro-arc oxidation ceramic coating were analyzed. The results showed that the corrosion resistance of the micro-arc oxidation ceramic coating in 3.5% NaCl solution was enhanced remarkably, the corrosion velocity was obviously slowed down. The thickness of micro-arc oxidation ceramic coating was about 11μm. The final phases in the coating were found to be α-Al2O3 and γ-Al2O3. The mechanism of the oxidation ceramic coating formation was investigated too.

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