Effect of Graphite on Tribological and Mechanical Properties of AA7075 Composites

The influence of graphite particulates on the dry sliding wear behavior of aluminum alloy 7075 (AA7075)-graphite composites has been evaluated using a pin-on-disc apparatus. The materials were fabricated by a liquid casting technique. Composites with 5-20 wt% graphite particles were processed. The casted composites were subjected to T6 heat treatment. The effect of sliding speed and sliding distance has been studied under dry sliding conditions. The hardness of the composites is measured using a Brinell hardness tester and their tensile strength is measured using a universal testing machine. The wear rate of the composites reduced with the addition of graphite content and reached a minimum with 5 wt% graphite content. The coefficient of friction is decreased with the addition of graphite content and reached a minimum at 5 wt% graphite. The effect of graphite on hardness and tensile strength is also studied. The worn surfaces of the pin specimen are analyzed with scanning electron microscopy. The 7075 aluminum alloy exhibited its potential to act effectively as a self-lubricating material under dry sliding conditions in the lower range of graphite content, and 5 wt% graphite appeared to be optimum.