scholarly journals Research of growth mechanism of ceramic coatings fabricated by micro-arc oxidation on magnesium alloys at high current mode

2015 ◽  
Vol 3 (3) ◽  
pp. 253-257 ◽  
Author(s):  
Wei-wei Chen ◽  
Ze-xin Wang ◽  
Lei Sun ◽  
Sheng Lu
Keyword(s):  
Magnesium Alloys ◽  
Growth Mechanism ◽  
Current Mode ◽  
Ceramic Coatings ◽  
High Current ◽  
Micro Arc Oxidation

Growth Process and Corrosion Resistance of Ceramic Coatings of Micro-Arc Oxidation on Mg-Nd Magnesium Alloys

2011 ◽  
Vol 189-193 ◽  
pp. 891-896
Author(s):  
Yong Chun Guo ◽  
Jian Ping Li ◽  
Jin Shan Li ◽  
Ping Wang
Keyword(s):  
Corrosion Resistance ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Magnesium Alloys ◽  
Phase Structure ◽  
Ceramic Coating ◽  
Ceramic Coatings ◽  
Ceramic Surface ◽  
Linear Regularity ◽  
Micro Arc Oxidation

The regulation of ceramic coating formed by micro-arc oxidation on Mg-3Nd-0.2Zn-0.4Zr(wt%) magnesium alloys has been investigated by SEM and XRD. The relation of phase structure and corrosion resistance of MgO coating formed by micro-arc oxidation in different growth stages has been analyzed. The results have shown that in the initial stages of micro-arc oxidation, the growth of coating accords with linear regularity, which is the stage of anodic oxidation controlled by electrochemical polarization. With elongated treated time and increased thickness of the coating, the growth of coating accords with parabolic and linear regularity, which is the stage of micro-arc oxidation. In the stage of local arc light, the slope of parabola and thickness of loose coating increases so that the growth rate enhances. The phase structure of loose coating is mainly composed of MgSiO3 and the phase structure of compact ceramic coating is mainly composed of MgO. From the stage of micro-arc oxidation to local arc light, corrosion resistance of coating firstly increase and then decrease. The satisfied corrosion resistance corresponds to the coating time ranging from 7 to15minutes.The addition of rare earth elements in the magnesium alloy reduces the amount of smooth areas on ceramic surface. So the ceramic coating becomes more compact and smooth. The rare earth elements don’t form independent phases in ceramic coating but affect the relative proportion of constitution phases, resulting in the reduction of intermixed magnesium phase and the increase of the MgO and MgSiO3 phases.

Variable Parameter Processes of Micro-Arc Oxidation for Aluminium Alloy

2011 ◽  
Vol 704-705 ◽  
pp. 1273-1278
Author(s):  
Cheng Gao ◽  
Jin Yong Xu ◽  
Xuan Yi Shi ◽  
Ya Juan Liu ◽  
Jing Chun Zhang ◽  
...  
Keyword(s):  
Growth Rate ◽  
Wear Rate ◽  
Ceramic Coating ◽  
Early Stage ◽  
Variable Parameter ◽  
Ceramic Coatings ◽  
Constant Current ◽  
Constant Voltage ◽  
Micro Arc Oxidation ◽  
The Way

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.

Protective and Thermophysical Characteristics of Plasma-Electrolytic Coatings on the Ultra-Light Magnesium Alloy

2021 ◽  
pp. 1-15
Author(s):  
Sergey Grigoriev ◽  
Igor Kondratsky ◽  
Boris Krit ◽  
Valery Ludin ◽  
Varvara Medvetskova ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Thermal Diffusivity ◽  
Magnesium Alloys ◽  
Ceramic Coatings ◽  
Specific Electrical Conductivity ◽  
Technological Parameters ◽  
Thermophysical Characteristics ◽  
Light Alloy ◽  
Plasma Electrolytic ◽  
Integral Assessment

Abstract Magnesium alloys are now widely used for various purposes due to their unique properties despite the significant disadvantage associated with low corrosion resistance. The plasma-electrolytic oxidation (PEO), which allows the formation of ceramic coatings on the surface of magnesium alloys, is the most advanced and effective method for their protection. But firstly, PEO process of magnesium alloys has some difficulties, and secondly, PEO coatings affect the thermophysical characteristics of the modified materials, in particular they reduce thermal diffusivity. The presented work is devoted to the development of the technological parameters for formation of protective coating on the ultra-light alloy Mg-8Li-1Al-0.6Ce-0.3Y by the PEO method. The results analyses of electrolytes acidity and specific electrical conductivity before and after PEO process and also investigation data of the coatings structure and surface morphology are presented. An integral assessment of the ability of thermal diffusivity and corrosion resistance of the modified alloy was made. Studying of protective and thermophysical characteristics of the obtained coating showed that it provides a sufficiently high corrosion protection, despite the relatively small thickness, and the presence of pores and slightly (not more than 5%) reduces the thermal diffusivity of the magnesium ultra-light alloy.

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