Characterization of micro arc oxidized 6082 aluminum alloy in an electrolyte containing carbon nanotubes

Abstract

In this study, micro arc oxidation (MAO) process was applied to 6082 aluminum alloy in an alkaline-based electrolyte with and without the addition of carbon nanotubes (CNTs) to the electrolyte. After oxidation, the coatings were investigated by a series of structural, morphological, and tribological tests to understand the effect of CNTs addition to the base electrolyte. X-ray diffraction analyses revealed that an oxide layer composed of α-Al2O3 and γ-Al2O3 in varying intensities was formed on the surface, and the addition of CNTs to the electrolyte may contribute to the formation of more α-Al2O3 after MAO for longer oxidation times. High-resolution SEM micrographs showed that CNTs were successfully incorporated into the pores of the alumina coating generated during the discharging stage of the MAO process. The addition of CNTs to the base electrolyte induced a rougher surface accompanied by a decrement in the coating thickness as compared to the sample treated in the base electrolyte. The surface hardness and dry sliding wear resistance of 6082 aluminum alloy increased by performing the MAO process in the base electrolyte, as expected, due to the formation of an alumina coating at the surface, and the addition of CNTs to the electrolyte resulted in a further increment in the coating hardness and dry sliding wear resistance.