Effects of duty cycle and pulse frequency on microstructures and properties of electrodeposited Ni–Co–SiC nanocoatings

Abstract

In this study, Ni–Co–SiC nanocoatings were fabricated using pulse current electrodeposition (PCE) method. Effects of duty cycle and pulse frequency on surface appearance, microstructure, phase structure, wear behavior, and corrosion resistance of as-deposited Ni–Co–SiC nanocoatings were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, nanoindentation, and both wear and corrosion tests. Results indicate that numerous small-sized grains formed on Ni–Co–SiC nanocoatings at 20% duty cycle to provide smooth, uniform, and fine microstructures. The content of SiC nanoparticles in Ni–Co–SiC nanocoatings decreased from 11.2 wt% to 7.4 wt% as duty cycle increased from 20% to 60%. However, the content of SiC nanoparticles in Ni–Co–SiC nanocoatings increased from 6.3 wt% to 9.7 wt% as pulse frequency increased from 100 Hz to 300 Hz. Ni–Co–SiC nanocoatings prepared at pulse frequency of 300 Hz and duty cycle of 20% exhibited average microhardness of 934.4 Hv and average thickness of 43.2 μm. Weight loss of Ni–Co–SiC nanocoatings at 300 Hz was only 17.2 mg, indicating significant wear resistance. In addition, Ni–Co–SiC nanocoatings produced at duty cycle of 20% and pulse frequency of 300 Hz exhibited the maximum impedance, indicating optimal corrosion resistance.