Influences of B4C and carbon nanotubes on friction and wear performance of Cu base self-lubricating composite

Mechanical and friction performance of Cu base composites strengthened by B4C and carbon nanotubes (CNTs) were investigated. The CNTs vary between 2 vol% -6 vol% and B4C proportion is a set number 2 vol%. SEM, EDS and TEM were applied to characterize the polished composite surface, worn surface, cross section of friction layer, and debris. The wear mechanisms of all samples were explored. Compared with pure copper, both the physical and wear properties of the composite are improved. The composite containing 4 vol% CNTs and 2 vol% B4C has the lowest, steadiest friction coefficient and the highest wear resistance among all materials. This is attributed to combining effects of B4C and CNTs with the proper proportion. It not only enhances the composite's mechanical properties, but promotes a continuous and uniform self-lubrication layer forming between friction pairs during the wear process. The wear mechanisms of pure Cu and composites (2, 4, 6 vol% CNTs) are severe plastic deformation and adhesion, abrasive wear, slight abrasive wear, abrasive and slight adhesive wear, respectively.