The effects of Cr and B doping on the mechanical properties and tribological behavior of multi-layered hydrogenated diamond-like carbon films

To enhance the adhesion strength and tribological properties of hydrogenated diamond-like carbon (H-DLC) films, the multi-layered H-DLC films consisting of a function layer with chromium and boron doping, Cr-C and Cr-H-DLC transition layer and a Cr bonding layer were prepared on 52100 steel through the unbalanced magnetron sputtering system. The influence of Cr and B doping on the mechanical properties and tribological performance were investigated. The results indicated that the structure of H-DLC, Cr-H-DLC and B-H-DLC films was compact. There were no peelingflake, delamination, and crack between the films and substrate. Raman spectra showed that the value of ID/IG increased with the Cr and B doping, which indicated that the sp3 content inside the H-DLC film decreased. Compared with the atmospheric condition, the coefficient of friction and wear rate of those films were higher than that in vacuum. According to the Raman spectra of the wear track, it was found that the graphitization of sliding interface theory had its limitations. The mechanical wear of those films was dominated by the abrasive and oxidative wear in the atmospheric environment. Owing to the passivation of the hydrogen atoms, the abrasive wear and adhesive wear was the main failure mechanism in vacuum. •With the doping of Cr and B, the multi-layered H-DLC films with compact microstructure were prepared.•The failure forms of doped film are abrasive and oxidative wear in air, while those are abrasive and adhesion wear in vacuum.•Based on characterization results, the traditional theoretical graphitization friction reduction mechanism has limitations.