Effect of BN fraction on the mechanical and tribological properties of Cu alloy/BN self-lubricating sleeves

Self-lubricating composite material sleeves were prepared using a powder matrix of 663-tin bronze powder in which boron nitride (BN) of 0 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, and 6 wt% was added as a lubricating phase. The microstructure, mechanical properties, and tribological performance of the samples were studied using optical microscopy, scanning electron microscopy, hardness tests, tensile tests, and wear tests. The results show that the density, hardness, and compressive strength of the samples each decrease gradually with the increase of BN content, and porosity increases with the increase of BN content. The friction coefficient and wear loss both reduced after BN was introduced in the Cu alloy matrix due to BN forming a lubricating film on the friction surface. With a BN content of 2 wt%, the sleeve showed the best combination of properties with a hardness of 55 HV, crushing strength of 302 MPa, density of 7.069 g/cm ³ , a relatively small friction coefficient and lowest wear loss. The new copper-based/BN self-lubricating composite material has good prospects for application in the manufacturing of frictional sleeves of high-speed sewing machinery.