Electrodeposited Ni-B/SiC micro- and nano-composite coatings: A comparative study

Abstract

Ni-B/SiC micro- and nano-composite coatings were electrodeposited in a modified watts bath containing SiC micro- and nano-particles with the average size of 3 μm and 100 nm, respectively. The chemical composition, SiC content; XSiC (wt.%), morphology, surface roughness, thickness, hardness and corrosion resistance of the deposited coatings were studied as a function of the particle concentration in the deposition bath (CSiC = 2, 4, 6, 8 g/L) and deposition current density (id = 0.5, 1, 2 and 3 A/dm2), using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Inductively Coupled Plasma (ICP), X-Ray Diffraction (XRD), microhardness measurements and potentiodynamic polarization (PP) tastings, respectively. The results indicated that the SiC content and surface roughness (Ra) of micro-composite coatings are increased with increasing both the CSiC and id and reached to the maximum of XSiC = 14.8 wt% and Ra = 4.58 μm at the CSiC = 8 g/L and id = 3 A/dm2. While the SiC content and roughness of nano-composite coating are initially increased and then decreased with increasing both the CSiC and id and the maximum of XSiC = 9.6 wt% and Ra = 2.28 μm were obtained at the CSiC = 4 g/L and id = 1 A/dm2. The thickness of both type of coatings increases almost linearly with id and micro-composite coatings exhibit greater thickness values. The nano-composites exhibit higher hardness and corrosion resistance than micro-composites despite having lower SiC contents. The maximum hardness and minimum corrosion resistance were 1035 HV and 0.03 μA/cm2 for micro- and 889 HV and 0.38 μA/cm2 for nan-composite coatings, respectively.