Wear behavior of aluminum matrix hybrid nanocomposites fabricated by powder metallurgy

In the present article, the dry sliding wear behavior of aluminum matrix nanocomposites containing various amounts of Al2O3-AlB12 (5,10 and 15 wt.%) particles was investigated. All specimens were prepared by mechanical milling of Al and Al2O3-AlB12 nanocomposite powders, followed by hot pressing. Wear tests were carried out at room temperature in air using the pin-on-disc machine under variable normal loads. The counterface was an AISI 52100 steel pin with the hardness of 780 HV. Friction values and wear mechanisms are discussed based on scanning electron microscopy observations and energy-dispersive spectroscopy analysis of wear tracks and wear debris morphology. The average hardness of the nanocomposite increased with the percentage of added Al2O3-AlB12 particles. Results confirmed that worn surfaces of all nanocomposite samples tested under variable loads, covered by a mechanically mixed layer (MML), contained a considerable amount of oxygen and iron. The results indicated that higher Al2O3-AlB12 content in the nanocomposite promotes stronger material transfer from the counterface and oxidation reaction and, consequently, causes formation of protective MML with higher amount of oxide compounds content on the worn surface of nanocomposite, leading to the lower wear rate. After a certain sliding distance, the friction coefficient of the nanocomposites reduced and tended to attain a constant value. The formation of MML on the worn surface which can act as a lubricant seems to be responsible for this trend. (C) 2011 Elsevier B.V. All rights reserved.