Friction and wear of Cu-15 wt%Ni-8 wt%Sn bronze lubricated by grease at room and elevated temperature

Cu-15 wt%Ni-8 wt%Sn (CuNiSn) bronze alloy shows promising bearing performance when used in tribological applications and has attracted increasing research interest. In this work, the tribological performance of CuNiSn in terms of friction and wear were investigated in a ball-on-disc contact configuration, sliding against a Al2O3 ball under varying normal loads (1 and 4 N) and environmental temperatures (room temperature (~18 °C) and 110 °C). Post-test characterization techniques, including optical profilometry, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM) were adopted to characterize the wear track on the CuNiSn surface after 13,500 cycles of reciprocating sliding. Both friction and wear behaviour was found to depend on the load and temperature whilst wear resistance reduced with increased temperature. A mechanically mixed layer (MML) and plastic deformation layer (PDL) were characterized by TEM micrographs of the cross-section from the wear track. Under 4 N load, a 1–1.5 μm thick tribolayer was developed during sliding at room temperature compared with a 200–300 nm tribolayer at 110 °C. The friction and wear mechanisms were largely dominated by properties of the tribolayers which were initially associated with and affected by load and temperature