Improving wear performance of CuSn5Bi5 alloys through forming self-organized graphene/Bi nanocomposite tribolayer

The wear and friction behavior of Pb-free Cu-Sn-Bi bearing alloys were improved by adding multi-layer graphene (MLG). An MLG/CuSn5Bi5 composite was produced by combining ball milling and conventional powder sintering. The composite exhibited increased bulk hardness and improved distribution and refinement of the Bi phase. Addition of MLG to the CuSn5Bi5 matrix resulted in a significant decrease in the friction coefficient and wear volume. Both adhesive and delamination wear were reduced at a certain MLG content. Despite an increase in the hardness, friction and wear improvements were caused by easy shear of the self-lubricating MLG in the contact interface, a decrease in the peeling of the brittle Bi phase, and the transport and spread of the Bi phase via slippage of the laminated MLG platelets on the worn surface. The self-organizing MLG/Bi nanocomposite tribolayer that forms is proposed to act as a lubricant and to improve the wear behavior significantly.