Tungsten Carbide/ Graphene Self-lubricating and Wear-resistant Coating

Thermal Sprayed tungsten carbide coating is a common wear-resistant coating with high microhardness and low oxide content. It has been widely used in aviation, machinery and other industrial fields. Because of the high hardness of the tungsten carbide coating, the friction coefficient of the friction system is large, which will cause serious wear and tear to the friction pairs matched with the tungsten carbide coating, even affect the service life of the wear-resistant protective coating.

Tungsten carbide spraying powder is the basis of preparing tungsten carbide wear-resistant coatings by thermal spraying. To prepare tungsten carbide wear-resistant coatings with self-lubricating properties, self-lubricating additives must be added to tungsten carbide spraying powder. At present, self-lubricating additives mainly include soft metals (Au, Ag, etc.), fluoride (LiF₂, CaF₂, etc.) and so on. The preparation of self-lubricating and wear-resistant tungsten carbide coatings containing modified graphene has been proposed by some scholars for disulfides (MoS2, WS2, etc.) and metal oxides (Zr₂O₃, Cr₂O₃, etc.).

The preparation of self-lubricating wear-resistant coating powder containing modified graphene tungsten carbide comprises the following steps:

（1）Graphene/nano-tungsten carbide composites were prepared by ultrasonic treatment of modified graphene/nano-tungsten carbide composites with a certain amount of ethanol.

（2）The mixed solution of modified graphene/nano-tungsten carbide composite and tungsten carbide/cobalt composite was obtained by adding a certain amount of tungsten carbide/cobalt sprayed powder into the mixed solution of graphene nano-tungsten carbide composite obtained and stirring with a vertical agitator at room temperature and rotating speed for a certain time.

（3）Tungsten carbide / cobalt spraying powder with modified graphene was prepared by vacuum freeze-drying in the mixed solution of modified graphene / nano-tungsten carbide composite and tungsten carbide / cobalt.

（4）Tungsten carbide/cobalt self-lubricating and wear-resisting coatings with modified graphene were prepared by thermal spraying on the surface of parts after cleaning and sandblasting.

It is found that the graphene in the nano-sheet layer distributes uniformly and dispersively in the coating, the graphene self-lubricating transfer film is formed on the worn surface continuously during the friction process, thus reducing the friction coefficient of the coating. To improve the wear resistance of the coating, it can be applied to the existing wearable parts to reduce anti-wear effect, it can also be applied to the hydraulic transmission components (plunger, piston, connecting rod) of the landing gear piston rod or construction machinery of the aircraft to replace the current electroplated hard chromium components, which can not only avoid the environmental pollution caused by hexavalent chromium particles. Moreover, the friction coefficient and wear rate in the friction process of the coating can be greatly reduced, and the working life of the parts can be increased under the worse environment.

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