Among the preparation methods of functional coatings, the electrodeposition technique has attracted much attention due to its advantages of economy, high efficiency and good structural adaptability. The application of aluminum alloy materials is greatly limited due to their poor friction reduction and wear resistance. Therefore, to enhance the tribological behaviors of aluminum alloy materials, the Ni-MoS2, Ni-SiC and Ni-MoS2/SiC composite coatings were prepared on the 2218 aluminum alloy by an electrodeposition technique. The prepared composite coating samples exhibited a compact and dense microstructure, which was consistent with the result of their high microhardness. No obvious microcracks and defects appeared at the interfaces, indicating that the composite coating samples had good adhesion to the substrates and can effectively improve the frictional shear resistance. The results of wear experiment showed that the wear rate, friction coefficient and friction response time of all composite coating samples were lower than that of the substrate sample. However, the friction reduction and wear resistance of the same composite coating sample were not consistent. The friction coefficient of the Ni-MoS2 composite coating sample was the lowest, and the wear rate of the Ni-SiC composite coating sample was the lowest. According to the worn surface observations, the wear mechanism of composite coating samples was mainly characterized by the mild abrasive wear, flake spalling, tearing and pits caused by particle shedding, and the substrate sample showed a severe adhesive wear and abrasive wear.

Electrodeposition has attracted tremendous interest in functional coatings due to its advantages of high efficiency, inexpensiveness and ease of implementation. In this work, nickel graphene oxide (Ni-GO), nickel silicon carbide (Ni-SiC) and nickel graphene oxide/silicon carbide (Ni-GO/SiC) composite coatings were electrodeposited on the 2218 aluminum alloy (2218AlA) substrate. The microstructure, microhardness, bonding strength and tribological behaviors of the composite coatings were carried out. According to the results obtained, the composite coatings were dense and compact, with no visible defects and microcracks, and well bonded to 2218AlA substrate. The microhardness of composite coatings was significantly increased compared to that of the 2218AlA substrate. The microhardness of Ni-SiC composite coating was the highest, reaching 3.14 times that of the 2218AlA substrate. The friction response time, friction coefficient and wear rate of the composite coatings were obviously lower. For the Ni-GO composite coating, the average friction coefficient is the smallest at 45.35% of the 2218AlA substrate, while the wear rate is the smallest at 46.97% of the 2218AlA substrate. However, the comprehensive tribological performances of the Ni-GO/SiC composite coating were superior. The abrasive and adhesive wear were the main wear mechanisms of composite coatings, but the degree of damage was different.