Investigation of dry sliding wear characteristics of Al 7075 reinforced with SiC-graphite hybrid composites: multi-parameter optimization using grey relational analysis

Metal matrix composites made of aluminium and ceramics reinforced with silicon carbide (SiC) have desirable mechanical characteristics. On the other hand, ceramic composites made of aluminium may need improvement in their lubricating and tribological properties. This study aims to develop a new material utilizing the powder metallurgy (P/M) technique by incorporating Graphite (Gr), which is self-lubricating. This research investigated the impact of Graphite on the wear characteristics of a hybrid composite material composed of Al 7075/SiC and varying percentages of Graphite (X = 0, 5, and 10 weight %). An experimental study was conducted to analyze the mechanical and wear properties of the hybrid composite. The hardness of Al7075 increased by 5% with 5 wt.% SiC compared to the base alloy. Adding 5 wt.% graphite to the Al7075/5 wt.% SiC composite increased hardness by 2.7% compared to the base alloy, but with 10 wt.% graphite, the hardness decreased below the base alloy. This decrease is likely due to graphite agglomeration, softer phases, and poor interfacial bonding. The wear characteristics of the composite were tested using the pin-on-disc method. Scanning electron microscopy (SEM) analysis of the hybrid composite revealed that the reinforcement particles were evenly distributed throughout the matrix. The tribological behaviour was optimized using the Taguchi design of experiments and the grey relational technique. The results showed a reduction in wear loss of around 25.08% and a reduction of the friction coefficient of about 54.37%. The results demonstrated that the hybrid composite composed of Al7075 with 5 wt.% SiC and 5 wt.% graphite outperformed the other hybrid composites regarding mechanical and tribological characteristics.