Effects of cathodic voltages on structure and wear resistance of plasma electrolytic oxidation coatings formed on aluminium alloy

Li, Qingbiao; Liang, Jun; Liu, Baixing; Peng, Zenghui; Wang, Qing

doi:10.1016/j.apsusc.2014.01.120

Cited by 85 publications

(44 citation statements)

References 31 publications

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“…The cathodic microdischarges would especially occur at the previous anodic microdischarges points because of the higher electrical field, 49 and thus causing a series of complex chemical, plasma chemical, and electrochemical reactions (Table III Eqs. [13][14][15][16][17], which led to the formation of microdischarge channels and the detachment of porous oxide. 50 When the current channeled through the point with lower resistance, the PEO coatings grew rapidly after the detachment of coatings.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, plasma electrolytic oxidation (PEO) is considered to be a well-known process for the in situ production of oxide coatings on Al and its alloys, which can offer better corrosion protection as compared to the other surface modification processes for substrate alloys. [1][2][3][4] In general, many processing factors, such as the composition of electrolyte, [5][6][7] additives, [8][9][10] applied power modes, [11][12][13] electrical parameters, 14,15 temperature, 16 and oxidation time, 17 are used to control the PEO process. These parameters not only affect the PEO process but also the performance of the prepared coatings.…”

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confidence: 99%

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Effect of the Cu Content on the Microstructure and Corrosion Behavior of PEO Coatings on Al–xCu Alloys

Zhu

Zhang

et al. 2018

J. Electrochem. Soc.

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In this study, scanning electron microscopy and electrochemical techniques were used to investigate the effect of the Cu content on the microstructure and corrosion resistance of plasma electrolytic oxidation (PEO) coatings on Al-xCu alloys. The results showed that Cu in the substrate alloy was used to promote the intensity and the transformation process of the microdischarges, which led to the undulating-ribbon feature of cross-sectional morphologies. The formation of pores and cracks in the coatings was facilitated by the oxygen release due to the oxidation of O 2− and the dissolution of copper oxide. Meanwhile, the average porosity of PEO coatings distinctly increased with the increase in the Cu content, which is the key factor causing the decreased corrosion resistance of PEO coatings. Due to their high strength to weight ratio, Cu-containing aluminum alloys are one of the most promising materials for use in aerospace and automobile applications. However, their application is limited by low corrosion resistance. Therefore, plasma electrolytic oxidation (PEO) is considered to be a well-known process for the in situ production of oxide coatings on Al and its alloys, which can offer better corrosion protection as compared to the other surface modification processes for substrate alloys. [1][2][3][4] In general, many processing factors, such as the composition of electrolyte, 5-7 additives, 8-10 applied power modes, 11-13 electrical parameters, 14,15 temperature, 16 and oxidation time, 17 are used to control the PEO process. These parameters not only affect the PEO process but also the performance of the prepared coatings. The characteristics of the formed PEO coatings could also be affected by the alloying elements in substrate alloys. However, this has not been studied in much detail. To the best of our knowledge, the literature contains several papers that describe the effect of multiple elements (such as Si, Mg, Cu, Li, and Fe) on the properties of the formed PEO coatings for commercial aluminum alloys.18-20 While, only a few studies focused on the effect of single alloying element in substrate. Among others, Ali et al. studied the PEO treatment of simple binary Al-Si alloys and reported that the thickness of PEO coatings significantly decreased, whereas their porosity increased with the increase in the Si content. The decomposition of volatile silicon oxides, such as SiO in the formed coatings during the PEO process, contributed to the high porosity. Furthermore, Si exhibits low electrical conductivity, which adversely affects the formation of microdischarges and the oxidation kinetics of the alloy. 21 Meanwhile, Oh et al. studied the effect of Mg on the properties of PEO coatings on Al-Mg alloys and demonstrated that when the amount of Mg was higher than 3 wt% the formation of α-Al 2 O 3 was inhibited.22 It is also reported that Zn is the primary alloying element for the 7××× series Al alloys, and the peculiar function of Zn during the formation of PEO coatings on binary Al-Zn alloys has also been investig...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Effect of the Cu Content on the Microstructure and Corrosion Behavior of PEO Coatings on Al–xCu Alloys

Zhu

Zhang

et al. 2018

J. Electrochem. Soc.

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“…Nevertheless, their applicability has been restricted due to their low hardness, poor wear resistance and high pitting corrosion tendency [3]. Different types of coatings such as nitrides [4,5], oxides [6], intermetallics [7,8] and composite [9] have been applied by diverse techniques such as mechanical coating [9], plasma electrolytic oxidation [10], ion implantation [11], plasma nitriding [12] and so forth to improve the surface characteristics of Al alloys. Among the nitride coatings, TiN [4,13] and AlN [5,14] have received a great deal of attention due to their excellent features.…”

Section: Introductionmentioning

confidence: 99%

Active screen plasma nitriding of Al using an iron cage: Characterization and evaluation

Yazdani

Soltanieh

Aghajani

2015

Vacuum

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“…The coating surface is porous and coarse, consisting of pancake-like structures with a central hole [7]. PEO coatings are divided into three layers, i.e., an outer loose layer, an inner dense layer, and the barrier layer near the substrate [8,9].…”

Section: Introductionmentioning

confidence: 99%

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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Effects of cathodic voltages on structure and wear resistance of plasma electrolytic oxidation coatings formed on aluminium alloy

Cited by 85 publications

References 31 publications

Effect of the Cu Content on the Microstructure and Corrosion Behavior of PEO Coatings on Al–xCu Alloys

Effect of the Cu Content on the Microstructure and Corrosion Behavior of PEO Coatings on Al–xCu Alloys

Active screen plasma nitriding of Al using an iron cage: Characterization and evaluation

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

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