Abstract:The design and preparation of aluminum alloy surface protective coating is one of the main methods to improve the surface hardness and corrosion resistance of aluminum alloy components. In this paper, a SiC/TiN particle reinforced Ni-Mo nanocomposite coating was prepared on the surface of 6061 aluminum alloy by pulse electrodeposition technique. By introducing SiC and TiN nanoparticles into the coating and changing the average current density and duty cycle of electrodeposition, the microstructure of the composite coating was adjusted, the film formation process and grain refinement mechanism of the nanoparticle-enhanced coating were analyzed. The relationship between the microstructure of composite coating and the corrosion resistance and wear resistance was studied. The results showed that the addition of double nanoparticles resulted in a shift of the coating structure from conical to cellular, and the grain size was reduced from 29.86 nm to 22.79 nm. The coatings prepared at current density of 8 A·dm-2 were the most homogeneous and dense with the highest SiC/TiN particle complexes of 1.3 wt% and 3.1 wt%, respectively. The coating exhibits (111) preferred orientation and typical FCC structure, with nanoparticles uniformly dispersed in a Ni-Mo matrix. The corrosion behavior of the coatings was investigated by Tafel polarization and immersion test. Compared with the corrosion current density of Ni-Mo composite coating of 7.08 μA/cm2, Ni-Mo/SiC-TiN nanocomposite coatings prepared at current densities of 4 A·dm-2, 8 A·dm-2, 12 A·dm-2 and duty cycle of 40% and 60% was 4.68 μA/cm2, 4.12 μA/cm2, 5.75 μA/cm2, 4.37 μA/cm2 and 5.53 μA/cm2, which were reduced by 34%, 42%, 19%, 38% and 21% respectively. In particular, the nanocomposite coatings prepared at the current density of 8 A·dm-2 and the duty cycle of 20% exhibited the best corrosion resistance. Compared with Ni-Mo coating, the introduction of SiC/TiN particles significantly improves the wear resistance of the coating. In addition, the mechanism of pulsed co-deposition is discussed in this paper.