Application Fields of ANOF Layers and Composites

Kurze, Peter; Krysmann, Waldemar; Schneider, H. G.

doi:10.1002/crat.2170211224

Cited by 67 publications

(28 citation statements)

References 2 publications

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“…Recently, spark anodizing, often also referred to as plasma electrolytic oxidation [7], anodic oxidation by spark discharge [8][9][10], anodic spark deposition [11] and micro-arc oxidation, has been attracted increased attention to improve surface properties, including corrosion, friction and biocompatibility, of titanium alloys [7,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Sparking proceeds during anodizing due to dielectric breakdown of the anodic oxide at high voltages.…”

Section: Introductionmentioning

confidence: 99%

Spark anodizing of β-Ti alloy for wear-resistant coating

Habazaki

Onodera

Fushimi

et al. 2007

Surface and Coatings Technology

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Spark anodizing of a bcc solid solution Ti-15% V-3% Al-3% Cr-3% Sn alloy has been performed in an alkaline electrolyte containing aluminate and phosphate using dc-biased ac anodizing to form a wear-resistant coating on the alloy. The coating consists mainly of Al 2 TiO 5 , with rutile and γ-Al 2 O 3 being present as minor oxide phases. Depth profiles of the coating, examined by glow discharge optical emission spectroscopy, have revealed that aluminium species, highly enriched in the coating, distribute uniformly in the coating, while phosphorus species, incorporated from the electrolyte, are located mainly in the inner part of the coating near to the coating/alloy interface. The location of the phosphorus species should be associated with porous nature of the coating, allowing access of the electrolyte directly to the inner parts of the coating. The porosity of the coating is reduced by anodizing to high voltages. The marked improvement of the wear resistance by the coating has been demonstrated from a pin-on-disc wear test.

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Section: Introductionmentioning

confidence: 99%

Spark anodizing of β-Ti alloy for wear-resistant coating

Habazaki

Onodera

Fushimi

et al. 2007

Surface and Coatings Technology

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“…1) of the distribution of the substance and the charge in the steam and gas vial is proposed. Some amount of hydrogen can exist in this region [14,15]. Numerous investigations [14,16,17] indicate that the model of the steam and gas vial is not sufficient to explain the processes that take place in the spark discharges in the metal-oxide-electrolyte system.…”

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confidence: 99%

“…Some amount of hydrogen can exist in this region [14,15]. Numerous investigations [14,16,17] indicate that the model of the steam and gas vial is not sufficient to explain the processes that take place in the spark discharges in the metal-oxide-electrolyte system. According to the theory of spark discharge, quick melting of the material and explosion-like ejection of its vapors takes place in the zones of the electrodes upon which the channel is supported.…”

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confidence: 99%

Simulation of synthesis of oxide-ceramic coatings in discharge channels of a metal-electrolyte system

Klapkiv¹

1999

Mater Sci

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The formation of oxide-ceramic coatings on rectifying metals in the metal-electrolyte system under the action of an external electric field includes several stages. The first stage consists in the formation of the primary oxide film according to the electrochemical mechanism. The electrochemical activity of the rectifying metals decreases in the row Mg, A1, Ti, Nb, Ta, and these metals remain at the beginning of the passivity row. A characteristic feature of the anodic behavior of the rectifying metals is the absence of the active region of dissolution, which is due to their electronic structure. In the metal-electrolyte systems, they give off their d-electrons and transform into ions with rearranged d-levels. These ions react with the oxygen dissolved in electrolyte, OH radicals, or water, forming surface oxide films. Anodic oxide films are amorphous and poreless, and they have ionic conductivity and high electrical resistance. They are classified [1] as n-semiconductors with a wide forbidden band. The electrons are not transferred through the passive layers on the rectifying metals [2,3]. The only reaction on the anode at a voltage of up to 100 V is the anodic growth of oxide. In this case, the overvoltage of the oxide formation is less than the voltage of the decomposition of the electrolyte. When the latter is reached, the injection of electrons into the oxide layer takes place, and oxygen begins to evolve on the anode [4]. This corresponds to the beginning of the second stage of the formation of the spark discharge channel in the metal-oxide-electrolyte system. The mechanisms of breakdown and the parameters of the discharge channel can be different [5,6], depending on the material of the electrode and the nature of the interelectrode space. In the case of realization of the spark discharge in the metal-oxide-electrolyte system under the action of a direct-current electric field, the metal serves as an anode, and the electrolyte serves as a cathode. The interelectrode space consists of the oxide and the double electric layer on the oxide-electrolyte boundary. The main drop of the potential is at the oxide interlayer where the electric field intensity is high [7]. At as low electric field intensity as 105 V/m, the high-energy electrons can cause the galvanoluminescence of the oxides [8]. For the electrons to have, under the action of the electric field, the acceleration necessary for breaking down the wide-band oxide, their energy must be higher than 3Eg/2 (Eg is the width of the forbidden band). These electrons have energy sufficient for ionizing the atoms, which results in the appearance of new electrons. When the coefficient of reproduction exceeds unity, electronic avalanche arises. The ionized atoms that remain behind the avalanche create a practically stationary spatial charge which decelerates the electrons. Since, as was mentioned above, the potential drop is localized mainly in the oxide, and the oxides of the rectifying metals show the properties of wide-band semiconductors of n-type, for determining...

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“…But in marine environment, its corrosion is fast and also pitting of surface further degrades its properties. The major techniques for solving these problems include electroplating, chemical plating, anodic oxidation, chemical conversion coatings, physical vapour deposition, surface coating and laser surface treatment and so on, but all of them have certain limitations (Robert and Alivait 1977;Dittrich et al 1984;Kurze and Krysmann 1986).…”

Section: Introductionmentioning

confidence: 99%

Ceramic coated Y1 magnesium alloy surfaces by microarc oxidation process for marine applications

2007

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The magnesium alloys occupy an important place in marine applications, but their poor corrosion resistance, wear resistance, hardness and so on, have limited their application. To meet these defects, some techniques are developed. Microarc oxidation is a one such recently developed surface treatment technology under anodic oxidation in which ceramic coating is directly formed on the surface of magnesium alloy, by which its surface property is greatly improved. In this paper, a dense ceramic oxide coating, ~20 μm thick, was prepared on an Y1 magnesium alloy through microarc oxidation in a Na 3 SiO 3 -Na 2 WO 4 -KOH-Na 2 EDTA electrolytic solution. The property of corrosion resistance of ceramic coating was studied by CS300P electrochemistry-corrosion workstation, and the main impact factor of the corrosion resistance was also analysed. Microstructure and phase composition were analysed by SEM and XRD. The microhardness of the coating was also measured. The basic mechanism of microarc coating formation is explained in brief.The results show that the corrosion resistance property of microarc oxidation coating on the Y1 magnesium surface is superior to the original samples in the 3⋅5 wt% NaCl solutions. The microarc oxidation coating is relatively dense and uniform, mainly composed of MgO, MgAl 2 O 4 and MgSiO 3 . The microhardness of the Y1 magnesium alloy surface attained 410 HV, which was much larger than that of the original Y1 magnesium alloy without microarc oxidation.

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Application Fields of ANOF Layers and Composites

Cited by 67 publications

References 2 publications

Spark anodizing of β-Ti alloy for wear-resistant coating

Spark anodizing of β-Ti alloy for wear-resistant coating

Simulation of synthesis of oxide-ceramic coatings in discharge channels of a metal-electrolyte system

Ceramic coated Y1 magnesium alloy surfaces by microarc oxidation process for marine applications

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