Application of factorial techniques to study the wear of Al hybrid composites with graphite addition

The wear and sliding friction response of a hybrid aluminium metal matrix composite reinforced with hard ceramic (5 wt.% of SiC) and soft solid lubricant (0, 5, and 10 wt.% of graphite) fabricated by powder metallurgy was investigated. The influence of the percentages of reinforcement, load, sliding speed and sliding distance on both the wear and friction coefficient were studied using the pin-on-disk method with tests based on the design of experiments. Analysis of variance (ANOVA) was used to investigate the influence of the parameters on both the wear rate and the coefficient of friction. The hardness of the composites decreases as the % of graphite (Gr) increases. The wear and friction coefficient were mainly influenced by both the sliding distance and the load applied. The morphology of the worn out surfaces and the wear debris was analysed to understand the wear mechanisms. The wear resistance of the hybrid composite containing 5 wt.% SiC and 5 wt.% graphite is superior to that of the graphite free composites and the other hybrid composites. This study reveals that the addition of both hard reinforcement like SiC and soft reinforcement like graphite improves the wear resistance of aluminium composites significantly. (C) 2012 Elsevier Ltd. All rights reserved.