The Effect Of The Design Of Multilayer Structure On The Mechanical Properties Of Si Doped Diamond Like Carbon Film

Si-doped DLC monolayer and multilayer films with different sub-layer modulus ratio and different sub-layer thickness ratio were prepared by ion beam sputtering(IBS). The effect of Si content in monolayer film, sub-layer modulus ratio and sub-layer thickness in multilayer films on the microstructure and mechanical properties of films were studied systematically. In addition, Ni and WS2 nanoparticles were added into PAO as additives for DLC based solid-liquid duplex lubricating firstly in this study. The effect of different nanoparticles lubricant on the tribological performance of solid-liquid lubrication system and its lubricating mechanism were studied systematically.(1) In this study, a series of DLC monolayer film with different Si doping content were prepared by ion beam sputtering. The results showed that because of the smaller C-Si bond energy than that of C-C, the internal stress of thin film reduced drastically. What is more, for the The film hardness and modulus decreased with the increasing of Si content. By doping Si, friction-reducing performance of the film was improved greatly, which mainly benefited from the generation of the Si-oxide transfer film after friction reaction.(2) Si doped DLC multilayer films with different sub-layer thickness ratio and sub-layer modulus ratio were deposited by ion beam sputtering. The results indicated that DLC multilayer films have obvious multilayer-structure, the total thickness was about 500 nm. Because the soft sub-layer can be served as buffer layer of hard layer to release internal stress, with the increasing of modulus ratio and the relative thickness of soft layer, the internal stress of multilayer film decreased. Since the soft layer was easier to blunt and deflect crack through plastic deformation, multilayer films’ hardness increased with the increasing of sub-layer modulus ratio, so as to the wear resistance. When every sub-layer thickness in a multilayer film was the same, the existence of the thicker monolayer could be avoided, which limited the growth of the crack interval, so the films hardness and wear resistance of multilayer with the same sublayer thickness were the best.(3) Ni and WS2 nanoparticles were added into PAO as additives for DLC based solid-liquid duplex lubricating firstly in this study. The results demonstrated that, for the monolayer film, because of its lower hardness, the friction-reducing and anti-wear performance were not obvious. But for the multilayer films, when adding Ni nanoparticles, its wear resistance was obvious. This is because Ni nanoparticles were so small that it could fill into the worn zone to avoid further wear. When adding WS2 nanoparticles into PAO, its friction-reducing and anti-wear performance were both prominent due to the generation of WO3 reaction film in the contact surface after friction test.