Overall performance of Ni-Co-WC nanocomposite coatings prepared by ultrasonic vibration-assisted scanning jet electrodeposition

To obtain a high-performance Ni-Co-WC nanocomposite coating on 45# steel, this work proposed a novel ultrasonic vibration-assisted scanning jet electrodeposition and used the range of WC nanoparticles concentration (3-12 g/L) in the electrolyte as the key variable in this study. Through harmonic response analysis, a 31 kHz frequency ultrasonic transducer was selected as the vibration source to achieve better vibration effects. The type of current mode that we employed was DC mode. The influence of ultrasonic vibration and the concentration of WC nanoparticles in the electrolyte on the surface morphology, micro-texture, microhardness, adhesion, and corrosion resistance of the nanocomposite coating were investigated by using SEM, XRD, Vickers microhardness tester, scratch tester and electrochemical workstation respectively. Compared to conventional scanning jet electrodeposition, the results indicated that the ultrasonic vibration improved the surface morphology, mechanical properties, and corrosion resistance of the coating, with the hardness increased by 15.9 % and the adhesion strength increased by 76.1 % as well as the corrosion current density decreased by 13.0 %. When the WC concentration in the electrolyte was 6 g/L, the Ni-Co-WC nanocomposite coating prepared by ultrasonic vibration-assisted composite scanning jet electrodeposition exhibited the best surface quality and properties. The microhardness of the coating was the highest at 590 HV, the adhesion strength was the largest at 33.4 N and the corrosion current density was as low as 4.104 μA·cm−2. Compared with the WC concentration of 3 g/L, when the WC concentration was 6 g/L, the hardness increased by 7.8 %, the adhesion strength increased by 41.5 % whereas the corrosion current density decreased by 30.6 %. In addition, molecular dynamics simulation was employed to calculate the effect of WC content in the coating on the binding energy between the coating and the substrate. The simulation results confirmed that the adhesive strength between the composite coating and substrate was directly proportional to the WC content in the composite coating. Therefore, this research is of great significance for the protection of offshore platform support structure materials and the improvement of their service life.