Ultralow friction and wear of alternating CrN/Cu3N multilayer coatings via tribocatalytically generated graphene

In response to the critical issues of delamination and cracking that plague CrN films within oil lubrication systems, this work designed and prepared multilayer alternating sputtering CrN/Cu 3 N films, and investigated the tribological properties under PAO10 lubrication, with particular emphasis on the influence of the composition, structure, coating arrangement and the mechanical properties of these films. The results showed that the composite film CrN/Cu 3 N (FH-Cu), which was alternately sputtered and capped with copper nitride, exhibited the optimal tribological properties, achieved a stable friction coefficient of 0.065 and the lowest wear rate (9.20 ×10 −8 mm 3 ·N −1 ·m −1 ). FIB-TEM analyses and Raman spectra indicated that a lubricating film containing graphene was in-situ generated at the friction interface. The DFT simulation results showed that the adsorption effect of copper nitride on the surface layer of the composite film FH (Cu) reduces the dissociation energy of PAO10 by 48 %. The results of differential charge density and Bader charge indicate that Cu 3 N (100) transfers 0.08e to PAO10 during friction, thereby demonstrating the frictional catalytic mechanism of Cu 3 N at the frictional interface. This work provides important insights into design of high-performance CrN/Cu 3 N composite films, highlighting the interactions among microstructure, catalytic activity, and friction-induced carbon films.