The tribological performance of ultra-hard ceramic composite coatings obtained through microarc oxidation

Krishna, L. Rama; Somaraju, K.R.C.; Sundararajan, G.

doi:10.1016/s0257-8972(02)00646-1

Cited by 216 publications

(91 citation statements)

References 11 publications

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“…[2] PEO technology is derived from conventional anodizing but uses environmental friendly solutions as electrolytes and the coatings exhibit improved wear and corrosion resistance. [3] The typical equipment for PEO treatment consists in a direct current (DC) power supply connected with a metallic tank, that works as cathode, and with the sample immersed in the electrolyte. During the process, an oxide film on the surface is immediately formed and when the potential exceeds the dielectric breakdown, the breakage of the weak parts of this film with the formation of micro-discharges occurs.…”

Section: Introductionmentioning

confidence: 99%

Corrosion properties of plasma electrolytic oxidation coated AA7075 treated using an electrolyte containing lanthanum‐salts

Pezzato

Brunelli

Dabalà

2016

Surface & Interface Analysis

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Plasma electrolytic oxidation (PEO) is a very promising process that can enhance the corrosion and wear resistance by producing a relatively thick, dense and hard oxide ceramic coating on light alloys. The improvement in the corrosion behaviour of the treated metals strongly depends on some process parameters: current density, voltage, treatment time and electrolyte composition. In particular, the addition of additives in the electrolyte produces significant changes in the corrosion behaviour. The use of rare earth salts, especially of cerium and lanthanum, during PEO treatment was already studied in literature and the use of these salts improved the corrosion resistance of the obtained coatings. However, only few works reported the dissolution of rare earth salts in the electrolyte, whereas in the majority of studies these salts are used in pre-treatment or post-treatment solutions.In this work, the effect of the dissolution in the electrolyte of various concentrations of lanthanum nitrate on the corrosion properties of PEO coated 7075 aluminium alloy was studied. The base electrolyte was an alkaline solution containing sodium silicate and different concentrations of lanthanum nitrate (0.025, 0.05, 0.075 and 0.1 g/l). All the samples were treated with high current densities and for short treatment times. The morphology, thickness and composition of the protective layer were studied with SEM, energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), glow-discharge optical emission spectroscopy and X-ray photoelectron spectroscopy (XPS). The corrosion resistance was evaluated performing potentiodynamic polarization tests and electrochemical impedance spectroscopy tests.PEO coatings obtained with additions between 0.05 and 0.075 g/l of lanthanum nitrate resulted more dense and adherent, as evidenced by SEM analysis. These additions of La(NO 3 ) 3 had a positive effect on the corrosion resistance causing the formation of a large passive zone.

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Section: Introductionmentioning

confidence: 99%

Corrosion properties of plasma electrolytic oxidation coated AA7075 treated using an electrolyte containing lanthanum‐salts

Pezzato

Brunelli

Dabalà

2016

Surface & Interface Analysis

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“…Even though the coatings are exposed to high temperatures, the metallic substrates are usually kept at relatively low temperatures; no degradation of mechanical properties of metallic substrates occurs during PEO. Thus, the PEO coatings are promising for corrosion protection of aluminium and magnesium [7][8][9][10][11][12][13][14][15][16][17][18], wear resistance of light metals and their alloys [9,[19][20][21][22][23][24][25][26][27][28][29][30], and improved biofunctionality of titanium [31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Two-step plasma electrolytic oxidation of Ti–15V–3Al–3Cr–3Sn for wear-resistant and adhesive coating

Tsunekawa

Aoki

Habazaki

2011

Surface and Coatings Technology

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Ti-15V-3Al-3Cr-3Sn (Ti-15-3) is one of the important practical titanium alloys with high cold deformability and high mechanical strength, but its wear resistance is poor. This paper reports the formation of wear-resistant and adhesive ceramic coatings on Ti-15-3 by two-step plasma electrolytic oxidation (PEO). The PEO of Ti-15-3 has been carried out first in alkaline aluminate electrolyte to form a wear-resistant oxide layer and then in acid electrolyte containing both phosphoric acid and sulphuric acid to improve adhesion of the coating. The coating formed in the alkaline aluminate electrolyte is more than 10 m thick, and highly crystalline. The main phase is Al 2 TiO 5 .This coating shows high wear resistance, but is not adherent to substrate due to the development of a number of voids and pores in the oxide layer close to the substrate. A new oxide layer with amorphous structure is formed next to the substrate in the subsequent PEO in the acid electrolyte, during which the voids are filled with a new 2 oxide formed in the acid electrolyte, reducing the porosity. As a consequence, the adhesion of the coating is markedly improved without deteriorating the high wear resistance.

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“…This ceramic coating could improve the corrosion resistance, wear resistance, and microhardness. [8][9][10] The MAO coating could easily be corroded by electrolyte ions because of the loose outer layer. Many sealing methods such as multilayer sol-gel coatings, SiO 2 -ZrO 2 sol-gel layer, and TiO 2 coating had been investigated.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of magnesium ions release, biocorrosion, and hemocompatibility of MAO/PLLA‐modified magnesium alloy WE42

et al. 2010

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Magnesium alloys may potentially be applied as biodegradable metallic materials in cardiovascular stent. However, the high corrosion rate hinders its clinical application. In this study, a new approach was adopted to control the corrosion rate by fabricating a biocompatible micro-arc oxidation/poly-L-lactic acid (MAO/PLLA) composite coating on the magnesium alloy WE42 substrate and the biocompatibility of the modified samples was investigated. The scanning electronic microscope (SEM) images were used to demonstrate the morphology of the samples before and after being submerged in hanks solution for 4 weeks. The degradation was evaluated through the magnesium ions release rate and electrochemical impedance spectroscopy (EIS) test. The biocompatibility of the samples was demonstrated by coagulation time and hemolysis behavior. The result shows that the poly-L-lactic acid (PLLA) effectively improved the corrosion resistance by sealing the microcracks and microholes on the surface of the MAO coating. The modified samples had good compatibility.

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The tribological performance of ultra-hard ceramic composite coatings obtained through microarc oxidation

Cited by 216 publications

References 11 publications

Corrosion properties of plasma electrolytic oxidation coated AA7075 treated using an electrolyte containing lanthanum‐salts

Corrosion properties of plasma electrolytic oxidation coated AA7075 treated using an electrolyte containing lanthanum‐salts

Two-step plasma electrolytic oxidation of Ti–15V–3Al–3Cr–3Sn for wear-resistant and adhesive coating

Evaluation of magnesium ions release, biocorrosion, and hemocompatibility of MAO/PLLA‐modified magnesium alloy WE42

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