Search

Diamond-like carbon (DLC) film is undoubtedly one excellent self-lubricating solid film to improve the fretting behavior due to its ultralow friction as well as high-hardness. Investigating the evolution laws of fretting running state with operating condition and the friction reduction mechanism of DLC film under fretting is vital for reducing friction and wear. Here, the fretting performance of self-mated hydrogen-containing DLC (H-DLC) and Cr-doped DLC (Cr-DLC) was studied under different normal loads and amplitudes. In addition, the mechanism of friction reduction for transfer film and the cause of discrepancy in fretting behavior were clarified through a control experiment. The results demonstrate that as the normal load increases, the relative slip decreases, the elastic deformation increases, and the fretting regime develops towards the partial slip regime, while the increasing amplitude moves the fretting regime towards slip regime. During fretting, the third body layer will transfer to the counterface, and form a uniform and graphitized transfer film. The difference in the length of run-in period and the sp2/sp3 hybrid carbon content of DLC films influences the formation rate and the graphitized degree of the transfer film, which induces the discrepancy of fretting behavior of H-DLC and Cr-DLC films. Thus, this study not only clarifies the evolution on fretting regime of DLC film with changes in working conditions, but also demonstrates the key role of highly graphitized transfer film in fretting performances of self-mated DLC films. This work demonstrates the controllability and potential of self-mated DLC films in the field of fretting. [Display omitted] • The evolution of fretting regime can be completed by adjusting the operating conditions, which can realize the reduction of friction and wear. • The control experiment explained the formation mechanisms of transfer film, and proved the relationship between graphitization and the fretting behavior. • The doping elements of DLC film will affect the hybrid carbon content of sp2/sp3 and the length of run-in period under fretting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Graphene oxide was modified by isopropyl triisostearyl titanate. • The composite coating was composed of MoS 2 film and well-dispersed graphene gear oil. • The composite coating exhibits excellent anti-friction/wear properties. • The mechanism relies on the formation of graphene-like transfer film. Single solid or liquid lubricant cannot meet the ever-increasing lubricating performance of mechanical motion under extreme operating conditions. Solid-liquid synergistic lubrication could effectively solve the friction and wear problems due to the cooperation of solid and liquid lubricant. Herein, the solid–liquid composite coating was prepared via molybdenum disulfide (MoS 2) film under graphene hybrid gear oil lubrication conditions. Its anti-friction and anti-wear abilities were reduced by 13.0% and 37.4% compared with gear oil lubricated MoS 2 film, and 46.7% and 97.1% lower than those of only MoS 2 film, respectively. More importantly, the graphene-like transfer film at frictional contact interfaces was formed. Hence, the excellent lubrication function of MoS 2 -based solid–liquid lubricating coating was attributed to not only the structural advantages of MoS 2 and graphene, but also the solid–liquid synergism and transfer film, thereby enhancing the interfacial load-bearing capacity and anti-friction/wear behaviors. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO)/molybdenum disulfide (MoS 2) heterostructure nanosheets (rGO-MoS 2 -1) were synthesized via vertically growing of MoS 2 on rGO skeleton using a facile one-pot hydrothermal method. Toward high-performance lubrication additive, the rGO-MoS 2 -1 in industrial gear oil shows extraordinary dispersity and stability because its steric hindrance effect restrains the aggregation and settling tendency. More importantly, its introduction can significantly reduce the friction (∼16.7%) and wear (up to 80%) under the sliding contact. The characterization and analysis on the worn surfaces reveal that good dispersion stability, the formation of rGO-MoS 2 -based lubrication protective film, and the lower shear strength induced by the inherent lattice mismatch between rGO and MoS 2 are the key factors in the friction reduction and protection the tribo-interfaces against wear. [Display omitted] • rGO-MoS 2 -1 heterostructured nanocomposite was successfully prepared by facile one-pot hydrothermal method. • rGO-MoS 2 -1 hybrid nanofluids display excellent dispersion stability, and friction reduction and wear resistance. • Excellent lubrication function mainly depends the incommensurately stacked 2D heterostructure and tribo-film. [ABSTRACT FROM AUTHOR]