Frictional Behaviour of Composite Anodized Layers on Aluminium Alloys

Three variants of the micro arc oxidation (MAO) technique have been used to treat a 2017A alloy surface. The first variant was a pure anodized layer, the second an anodized layer with SiC embedded nanoparticles and the third an anodized layer with Si₃N₄ nanoparticles. Tribological tests were performed for all variants, on three samples for every case. Friction coefficients and wear rates were calculated on the basis of experiments. The pure anodized layer manifested friction coefficient values within the range of 0.48 ÷ 0.52 and a wear rate in the range ~10^-15 m³N^-1m^-1. SiC nanoparticles improved the tribological properties of the layer, as indicated by a reduction of the friction coefficient values to the range of 0.20 ÷ 0.26 with preserved very high resistance against wear (wear rate ~10^-15 m³N^-1m^-1). Si₃N₄ particles embedded in anodized layer deteriorated the tribological properties, with a reduction in the resistance against fatigue and wear, intensification of friction forces and a change in the nature of friction contact behavior to more abrasive-like nature (friction coefficients ranging from 0.4 to 0.6 and wear rates ~10^-14 m³N^-1m^-1).