Tribological and Nano-Scratch Properties of Aluminum (A356) Based Hybrid Composites Reinforced with MWCNTs/Alumina Fiber

In this article, the tribological properties of aluminum/MWCNTs/Al₂O_3sf hybrid composites with varying volume fraction of 10 vol%, 15 vol% and 20 vol% was investigated under dry sliding conditions. The experiments were performed according to design of experiments approach using Taguchi method to predict the wear properties of composites. The results indicated that the composites of 15 vol% had lower wear loss, whereas the coefficient of friction (COF) decreased significantly at 20 vol%. Taguchi based ANOVA analysis showed that the sliding distance was found to be the prominent factor controlling the wear loss; applied load influenced COF most significantly. It could also be noticed that the COF and wear loss increases with an increase in sliding load and sliding distance. The decrease in wear loss and the COF can be attributed to the self-lubrication effect of MWCNTs, and the combined effect of reinforcements in the composites. In addition, nanoscratch test was performed to determine the COF and the effect of the reinforcements on local regions of the composites. The results revealed that higher friction force was obtained near the regions of MWCNTs and Al₂O_3sf while nanoscratching. The COF of composites of 20 vol% was found to slightly higher compared to that of 10 vol% and 15 vol%. This is attributed to the presence of MWCNTs cluster within the Al₂O_3sf network results prevent the micro-plastic deformation of Al matrix, and the formation of tribofilms with nanoscaled thickness in the scratch region. These friction and wear results indicate that the presence of a limited amount and size of MWCNTs clusters are beneficial to the tribological properties of the hybrid composites.