Effect of Ultrasonic Power on Microstructure and Properties of Ultrasonic-Assisted Electrodeposited Ni–Al2O3Thin Nanocoatings

In this work, Ni–Al2O3thin nanocoatings (TNCs) containing γ-Al2O3nanoparticles were fabricated by ultrasonic-agitated electrodeposition (UAE). The influence of ultrasonic power on the microstructure, surface topography, phase structure, microhardness, and wear and corrosion performance was also discussed in detail. These results demonstrated that ultrasonic power had a considerable influence on the surface microstructures of the Ni–Al2O3TNCs. At an ultrasonic power of 300 W, the microstructure of the NA-3 TNC changed significantly; the surface was compact, fine, and smooth in the micro-area and contained the highest level of Al2O3(9.9 wt%). Diffraction peaks of the Ni grains in all Ni–Al2O3TNCs appeared at 44.65°, 52.20°, 76.85°, and 92.55° assigned to the (1 1 1), (2 0 0), (2 2 0), and (3 1 1) planes, respectively, and corresponded to a face-centered cubic structure. The microhardness values of the Ni–Al2O3TNCs initially increased before decreasing slightly as the ultrasonic power increased from 100 to 400 W. The NA-3 TNC had the highest microhardness (~ 916.2 Hv) among the Ni-Al2O3TNCs tested. Furthermore, the NA-3 TNC processed the lowest corrosion current density (0.034 µA/mm2) and the highest maximum corrosion resistance. The average wear rate for the NA-3 TNC was only 26.1 mg/min.