Friction, wear and plastic deformation of Cu and α/β brass under lubrication conditions

• The improved tribological properties of Cu in comparison to brass.
• Superplastic deformation of α-phase grains of brass.
• Intragranular sliding in α-phase with formation of voids and cracks.
• Deformation of Cu localized at thin surface layers.
• Thickness of wear particles of brass closed to the size of shear bands.

Friction, wear and plastic deformation of copper (Cu) and α/β brass were studied under lubrication conditions. Hardness and microstructure of surface layers were evaluated. The friction properties were presented by Stribeck curves. The friction coefficient and wear of brass were significantly larger in comparison to Cu. The critical load of transition from the elasto-hydrodynamic lubrication (EHL) to boundary lubrication (BL) was two times lower for brass. Superplastic deformation of α-phase grains in brass is appeared under friction in BL, whereas plastic deformation localized at thin surface layers is observed for Cu. Intragranular sliding in α-phase is accompanied with the formation of shear bands and many pores coalesced to cracks. Thickness of the wear particles of brass is close to the width of shear bands. The deformation hardness of brass is significantly higher in comparison to Cu rubbed in the BL region.