Technological Aspects of Synthesizing Ceramic Coatings by Flow-Through Micro-Arc Oxidation

In micro-arc oxidation process, ceramic coating had a rapid growth all along by the way of constant current oxidation, and ceramic coating had a low roughness by the way of constant voltage oxidation. But few research focus on the mixed control process of constant current oxidation and constant voltage oxidation. In this paper we propose a variable parameter process that can combine the advantages of constant current and constant voltage oxidation for the first time. The growth kinetics of different technics was analyzed according to the change law of current and voltage. Surface topographs of ceramic coating were observed using scanning electron microscopy (SEM). The friction tests were carried out using a self-made friction tester. The results show that ceramic coating has an upper growth rate and a low roughness by the process of constant current+constant voltage oxidation. The ceramic coating has a high growth rate by process of constant voltage+constant current oxidation. The results of friction test indicate that the wear rate and roughness of ceramic coating are positive correlation at early stage of friction. While the ceramic coatings treated by different technics have the close wear rate at stable friction stage, which embodies the inner layer of ceramic coating has a well antiwear behavior.

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The Gas Permeability of Plasma Sprayed Ceramic Coatings

Thermal Spray 1997: Proceedings from the United Thermal Spray Conference ◽

10.31399/asm.cp.itsc1997p0483 ◽

1997 ◽

Author(s):

A.C. Fox ◽

T.W. Clyne

Keyword(s):

Gas Permeability ◽

Test Procedure ◽

Ceramic Coatings ◽

Hydrogen Gas ◽

Steady State Flow ◽

Flow Rates ◽

Specific Permeability ◽

Measured Flow ◽

Flow Through ◽

Plasma Sprayed

Abstract A simple test procedure, based on steady state flow through a membrane, has been developed for measurement of the gas permeability of specimens over a range of temperature. The reliability of this equipment has been verified by testing solid disks containing single perforations and comparing the measured flow rates with those expected on the basis of laminar flow. Coatings of yttria-stabilised zirconia have been produced by plasma spraying in vacuum and in air. The specific permeability of these coatings has been measured at temperatures ranging up to 600°C, using hydrogen gas. It has been found that permeability is increased for coatings produced with longer stand-off distances and at higher pressures. Porosity levels have been measured using densitometry and microstructural features have been examined using SEM. A model has been developed for prediction of the permeability from such microstructural features, based on percolation theory. Agreement between predicted and measured permeabilities is good, although it is clear that more comprehensive data are needed in order to validate the model systematically.

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The Improved Friction Properties of Bonded MoS2 Films by MAO Treating of Al Substrate

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.275-277.1911 ◽

2013 ◽

Vol 275-277 ◽

pp. 1911-1914 ◽

Cited By ~ 1

Author(s):

Han Jun Hu ◽

Hui Zhou ◽

Yu Gang Zheng ◽

Kai Feng Zhang ◽

Zhi Hua Wan

Keyword(s):

Tribological Properties ◽

Solid Lubricants ◽

Ceramic Coatings ◽

Test System ◽

Test Method ◽

Test Results ◽

Specimen Test ◽

Micro Arc Oxidation ◽

A New Technique ◽

Porous Microstructures

The bonded MoS2 films are widely used as solid lubricants in aerospace mechanisms due to their excellent tribological properties. Traditionally, the MoS2 was directly bonded on the Al substrate that was only treated by the technique named of sandblast. For improving the tribological properties of MoS2 films, micro arc oxidation (MAO) instead of sandblast was introduced as a new technique for treating of Al substrate. In this article, the tribological properties of MoS2 films which were bonded on different surface of Al substrate as mentioned above were discussed, respectively. It was concluded from the test results that the MoS2 films bonded on substrate treated by MAO have better tribological properties than those samples treated by sandblast. The endurance life against abrasion of the former is as high as twenty times of the latter by the stand test method of ball on disk using the UMT Multi-Specimen Test System. This test results could be illustrated by the following reasons. The first is the porous microstructures of MAO ceramic coatings on the Al substrate. The coatings have numerous pits to be good at increasing the binding force with the MoS2 films, and the pits can also provide a MoS2 lubricants reservoir during processes of friction. Both of them improved the MoS2 film’s ability of wear-protective. The second is that hardness of the coating is higher than the Al, and this ensures well wearing resistance, especially in practical application to big load-supporting moving parts, such as bearing, gear, etc…

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The Characteristic of Ceramic Coatings Prepared on Magnesium Alloy AZ91D by Micro-Arc Oxidization in Silicate Electrolyte

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.146-147.941 ◽

2010 ◽

Vol 146-147 ◽

pp. 941-947

Author(s):

Xi Chang Shi ◽

Xiang Xiao ◽

Bai Zhen Chen ◽

Wei Shang

Keyword(s):

Magnesium Alloy ◽

Outer Region ◽

Ceramic Coatings ◽

Nacl Solution ◽

Acacia Gum ◽

Alloy Az91d ◽

Micro Arc Oxidation ◽

Distribution Phase ◽

Magnesium Surface ◽

Better Than

A novel process of micro-arc oxidation (MAO) on AZ91D magnesium alloy is investigated in a Na2SiO3-NaOH-montmorillonite-EDTA-acacia gum electrolyte solution. The morphologies, elements distribution, phase components of the coatings are characterized by SEM, EDS and XRD. And CHI600 electrochemistry corrosion workstation is employed to investigate the property of corrosion resistance of the coatings. Furthermore, the anti-corrosion behavior is analyzed immersed in 3.5 wt. % NaCl solution. The results reveal that the ceramic coatings have the relatively dense and uniform in thickness and the silicon element tends to present primarily in the outer region of the coatings. The XRD results indicate that the oxide films are mainly composed of Mg2SiO4 and MgAl2O4 phases. The immersion results show that the corrosion resistances of the ceramic coatings on AZ91D magnesium surface are better than the magnesium substrate.

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Formation of Wear- and Corrosion-Resistant Ceramic Coatings by Combined Technologies of Spraying and Micro-Arc Oxidation

Russian Journal of Applied Chemistry ◽

10.1134/s1070427219070012 ◽

2019 ◽

Vol 92 (7) ◽

pp. 875-882 ◽

Cited By ~ 2

Author(s):

Yu. A. Kuznetsov ◽

M. A. Markov ◽

A. V. Krasikov ◽

R. Yu. Bystrov ◽

A. N. Belyakov ◽

...

Keyword(s):

Ceramic Coatings ◽

Corrosion Resistant ◽

Wear And Corrosion ◽

Micro Arc Oxidation ◽

Resistant Ceramic

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Morphology and Wear Resistance of Composite Coatings Formed on a TA2 Substrate Using Hot-Dip Aluminising and Micro-Arc Oxidation Technologies

Materials ◽

10.3390/ma12050799 ◽

2019 ◽

Vol 12 (5) ◽

pp. 799 ◽

Cited By ~ 5

Author(s):

Shaopeng Wang ◽

Lian Zhou ◽

Changjiu Li ◽

Zhengxian Li ◽

Hongzhan Li

Keyword(s):

Wear Resistance ◽

Surface Composition ◽

Pure Titanium ◽

Titanium Substrate ◽

Ceramic Coatings ◽

Oxide Ceramic ◽

Pure Aluminium ◽

X Ray ◽

Micro Arc Oxidation

Aluminium layers were coated onto the surface of pure titanium using hot-dip aluminising technology, and then the aluminium layers were in situ oxidised to form oxide ceramic coatings, using the micro-arc oxidation (MAO) technique. The microstructure and composition distribution of the hot-dip aluminium coatings and ceramic layers were studied by using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The phase structure of the MAO layers was studied using X-ray diffraction. The surface composition of the MAO layer was studied by X-ray photoelectron spectroscopy. The wear resistance of the pure titanium substrate and the ceramic layers coated on its surface were evaluated by using the ball-on-disc wear method. Therefore, aluminising coatings, which consist of a diffusion layer and a pure aluminium layer, could be formed on pure titanium substrates using the hot-dip aluminising method. The MAO method enabled the in-situ oxidation of hot-dip pure aluminium layers, which subsequently led to the formation of ceramic layers. Moreover, the wear resistance values of the ceramic layers were significantly higher than that of the pure titanium substrate.

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