Electrolytic Deposition Behaviors of Ni-SiC Composite Coatings Containing Submicron-Sized SiC Particles

Abstract

Submicron-sized SiC particles (130 nm mean diameter) were codeposited with nickel by electrolytic plating in a nickel sulfamate bath to from Ni−SiC composite coatings. The effects of plating parameters, such as pH of the plating bath, SiC content in the plating bath, stirring rate, and current density on the deposition behaviors of Ni−SiC composite coatings were investigated. Results revealed that zeta potential decreased with increasing pH; the iso-electric point was measured to be }7.0 in pH. The codeposition of SiC increased with increasing pH, and the deposition rate increased with increasing SiC content in the plating bath. This may be due to the increased flux of approaching SiC particle towards the cathode due to enhanced SiC content in the plating bath. The codeposition of SiC exhibited a maximum at the stirring rate of 100 rpm. This can be explained by hydrodynamic effects and particle characteristics. The deposition rate increased with increasing current density. The codeposition of SiC increased up to a maximum of 15 A/dm2 and then decreased This can be explained by electrophoretic movement of the SiC particles due to the adsorption of nickel ions and protons in the plating bath on the SiC particle surface. Submicron-sized SiC particles provided for a rough plating surface. This effect may be attributable to the strong tendency of submicron-sized SiC particles to agglomerate in the plating bath.