An investigation of ceramic coating growth mechanisms in plasma electrolytic oxidation (PEO) processing

Hussein, R.O.; Nie, Xueyuan; Northwood, Derek O.

doi:10.1016/j.electacta.2013.08.137

Cited by 419 publications

(183 citation statements)

References 22 publications

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“…The larger nodules at the surface (Figure 2b) indicated an increased area and a longer duration of the molten zone, which was caused by a stronger discharge. Additionally, as shown in Figures 1b and 2b, trench-like open pores were present in the center of the molten-shaped products, which was very common and usually appeared in the thinner PEO coatings on Al [38], Mg [31], and Ti [6]. A reasonable explanation for the open pores was that the amount of molten products was insufficient to complement the plasma discharge channels in the cooling process.…”

Section: Growth Model Of Peo Coatingmentioning

confidence: 94%

“…The EDS results (Figures 1e,f and 4) confirmed that nodules were Si-rich products of electrolyte deposits and that the molten-shaped products were mainly oxides of the substrate. The different morphologies and components at the surface were ascribed to various kinds of discharges in the integrated discharge model [30][31][32]. Additionally, a~1 µm barrier layer that consists of dense cells was present at the aluminum/coating interface.…”

Section: The Formation Process For 3d Structures Of Peo Coatingmentioning

confidence: 99%

“…Various growth models were proposed based on these mechanisms to describe the formation of the PEO coating [30][31][32]36]. These models illustrated the origins of plasma discharges and the relationship between discharges and coating structure.…”

Section: Growth Model Of Peo Coatingmentioning

confidence: 99%

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Evolution of the Three-Dimensional Structure and Growth Model of Plasma Electrolytic Oxidation Coatings on 1060 Aluminum Alloy

Liu

Wang

et al. 2018

Coatings

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Abstract:A deeper understanding of plasma electrolytic oxidation (PEO) can in turn shed light on the evolution of coating structures during such oxidation processes. Here, a three-dimensional (3D) structure of PEO coating was investigated based on the morphologies at different locations in a PEO coating and on the elemental distribution along certain sections. The coating surface was dominated by a crater-or pancake-like structure of alumina surrounded by Si-rich nodules. A barrier layer with a thickness of~1 µm consisting of clustered cells was present at the aluminum/coating interface. As the coating thickened, the PEO coating gradually evolved into a distinct three-layer structure, which included a barrier layer, an internal structure with numerous closed holes, and an outer layer with a rough surface. During the PEO process, molten zones formed along with the plasma discharges. The volume and lifetime of the molten zones changed with oxidation time. The diversities of cooling rates around the molten zones resulted in structural differences along a certain section of the coating. A growth and discharge model of PEO coatings was established based on the 3D structure of the particular coating studied herein.

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Section: Growth Model Of Peo Coatingmentioning

confidence: 94%

Section: The Formation Process For 3d Structures Of Peo Coatingmentioning

confidence: 99%

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Evolution of the Three-Dimensional Structure and Growth Model of Plasma Electrolytic Oxidation Coatings on 1060 Aluminum Alloy

Liu

Wang

et al. 2018

Coatings

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“…As a result of the PEO coating process, the magnesium alloy surface is converted into ceramic-like coating layers that are hard, well adhered to the substrate and wear resistant [12,13]. PEO coatings mechanical and tribological properties depend on the characteristics schematically shown in Fig.…”

Section: Mechanical/tribological Propertiesmentioning

confidence: 99%

Plasma electrolytic oxidation (PEO) coatings on Mg-alloys for improved wear and corrosion resistance

Hussein¹,

Nie²,

Northwood³

2015

Surface and Contact Mechanics Including Tribology XII

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Due to their high chemical reactivity, relatively low melting point and low hardness, magnesium and magnesium alloys have relatively poor corrosion and wear resistance. Since both corrosion and wear are surface phenomena, a number of surface engineering techniques have been used to improve corrosion and wear performance. Whilst some surface hardening/strengthening methods have led to improvements in wear properties, they have not, in themselves, significantly improved the corrosion performance. Plasma electrolytic oxidation (PEO) has the potential to produce hard, compact oxide coatings that are well adhered to the magnesium alloy substrate. Such coatings can provide both improved wear and corrosion resistance. In this paper we describe how by changing the PEO processing parameters (substrate alloy; electrolyte; current or voltage; processing time) we can change the nature of the PEO oxide coatings (thickness; microstructure; porosity; phase content; composition) which, in turn, effects the corrosion and wear performance. All PEO-coatings have a three-layer structure with a porous outer layer, and intermediate dense layer and a thin inner dense layer. From a corrosion aspect, the performance of coatings is determined by the time taken for corrosion to initiate since this is much shorter than time taken for the coating to degrade. For PEO-coated Mg-alloys, this initiation time is primarily determined by the thickness, porosity and phase content of the inner dense layer at the coating/substrate interface. With respect to tribological properties, the coefficient of friction (COF) in dry sliding wear increases with increasing surface roughness of the PEO coatings. The wear rate is primarily determined by the thickness and hardness of the intermediate dense layer.

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“…Bu katkılar mikro ark oluşum gerilimini düşürerek işlem süresini kısaltır ve kaplama kalitesini iyileştirirler. Diğer taraftan, elektrolite katılan bazı bileşenler kaplama büyüme hızını ve kalınlığını arttırırlar [6]- [8].…”

Section: Introductionunclassified

Structural and wear behavior of coatings formed on AA7075 aluminum alloy by plasma electrolytic oxidation

Karaoğlu¹,

Sonuvar²

2017

Pamukkale J Eng Sci

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An investigation of ceramic coating growth mechanisms in plasma electrolytic oxidation (PEO) processing

Cited by 419 publications

References 22 publications

Evolution of the Three-Dimensional Structure and Growth Model of Plasma Electrolytic Oxidation Coatings on 1060 Aluminum Alloy

Evolution of the Three-Dimensional Structure and Growth Model of Plasma Electrolytic Oxidation Coatings on 1060 Aluminum Alloy

Plasma electrolytic oxidation (PEO) coatings on Mg-alloys for improved wear and corrosion resistance

Structural and wear behavior of coatings formed on AA7075 aluminum alloy by plasma electrolytic oxidation

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