| Friction exists in almost all mechanical systems with moving parts,causing a large amount of energy dissipation,material loss and carbon dioxide emissions every year.The development of advanced lubrication systems for aerospace,automotive,military and various industrial applications has become an urgent task worldwide.Lubricants are generally used to improve this situation,but under boundary lubrication conditions,the load-bearing capacity and antiwear properties of lubricating oils are insufficient.Basic lubricating oil additives have become a rapidly developing research field in recent years.Diamond-like carbon-based(DLC)films have excellent mechanical and tribological properties and are expected to be ideally applied in various engineering fields.However,the tribological properties of DLC film are extremely sensitive to the environment and working conditions,and cannot effectively protect materials or mechanical moving parts that require lubrication under a wide range of working conditions.Therefore,it is necessary to modify the surface of the DLC film to meet the increasingly stringent requirements of the related tribological field.It will be a good choice to introduce composite additives in the fields of liquid oil lubrication and solid lubrication.In this paper,the frictional properties of 3D graphene/hexagonal boron nitride composites as lubricant additives and solid additives on steel substrates and DLC films were studied respectively.The synergistic lubrication mechanism of composite materials under different lubrication conditions was discussed.The main contents and results of this study are as follows:(1)Firstly,add the 3D graphene and h-BN to the dispersant(span-80)separately,mixing them in different proportions,and select the best dispersion performance through observation.Then,the frictional properties of 3D graphene,h-BN with different mass fractions and the mixture of the two are studied respectively.The study found that when 3D graphene and h-BN are used in combination,the friction coefficient and the wear rate of steel balls are the best compared to a single additive.It is verified that 3D graphene and h-BN have obvious synergistic lubrication effects.(2)Disperse 3D graphene and h-BN into ethanol separately,and mix them uniformly by ultrasonic to prepare 3D graphene/h-BN composite nanomaterials.For lubricating additives with different mass fractions and different load conditions,under the steel-DLC friction pair did an evaluation.The results indicate that the lubricating performance of 3D graphene/h-BN composite nanomaterials is better than single additives,which is mainly due to the formation of friction transfer film on the steel ball.The presence of the transfer film effectively prevents the direct contact between the steel ball and the surface of the DLC film,which improves the performance of the DLC film under contact conditions of room temperature.(3)In view of the excellent performance of 3D graphene/h-BN composites as solid lubricants,the friction properties of 3D graphene/h-BN composites under steel/hydrogen containing amorphous carbon film(a-C:H)were studied.The results show that when 3D graphene and h-BN are used as a single-component lubricant combined with a-C:H film,their lubricating properties are not optimal,and some even play an antagonistic role.When under the action of the 3D graphene/h-BN composite material,the friction and wear rate are reduced to a minimum.This is mainly due to the tribo-chemical reaction caused by the 3D graphene/h-BN composite material to form lubrication carbon phase,thereby reducing the shear strength of the contact area. |
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