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Characterization and wear- and corrosion-resistance of microarc oxidation ceramic coatings on aluminum alloy

2004; Elsevier BV; Volume: 389; Issue: 1-2 Linguagem: Inglês

10.1016/j.jallcom.2004.05.084

1873-4669

Tongbo Wei, Fengyuan Yan, Jun Tian,

Aluminum Alloys Composites Properties

Thick and hard ceramic coatings were prepared on Al–Cu–Mg alloy (2024 Al alloy) making use of microarc oxidation in an alkali-silicate electrolytic solution. The microstructure, phase composition, corrosion resistance friction and wear behaviors of the microarc oxidation coatings and the impact toughness of the impacted Al alloy blocks were investigated. Moreover, the corroded surfaces and the impacted surfaces and cross-sections of the microarc oxidation coatings were observed with a scanning electron microscope. The results show that the microarc oxidation coatings can be divided into a porous loose outer region consisting predominantly of γ-Al2O3 and AlSiO phase and a dense internal region consisting predominantly of α-Al2O3. They have excellent corrosion resistance, though the thicker coating shows somewhat poorer corrosion-resistance than the thinner one. The differences in the corrosion-resistance of the microarc oxidation coatings with different thicknesses are related to their different microstructures. The impact toughness of the Al alloy substrate is decreased after modification with the microarc oxidation coatings of extremely high hardness. This implies that the microarc oxidation coatings on the Al alloy substrate may not be suitable to impacting working condition. After abrasion away of the loose outer layer, the polished compact inner coatings possess excellent wear- and corrosion-resistance and strong adhesion to the substrate, and they show further significantly improved wear-resistance under the lubrication of a commercial 4838 lubricating oil. Namely, the friction coefficient and wear rate of the polished 100 μm coating under the oil-lubricated-condition are reduced to be 1/10 and 1/1000 of that under dry sliding. The microarc oxidation coatings mainly composed of hard α-Al2O3 could find promising application in preventing the corrosion and wear of Al alloy-based components.