Influence of Size and Dispersion of SiC Particles in the Preparation of Ni-P-SiC Composite Plating

The composite plating, in which SiC particles were codeposited in Ni-P alloy coating by a chemical plating technique, was investigated with emphasis on the effects of size and dispersion of SiC particles. When fine SiC particles with an average size of 0.27μm were used, the deposition quantity of composite coating showed a maximum at a certain reaction time, and large agglomerates consisting of SiC particles and Ni-P phase were formed on the plated surface. The release of agglomerates from a substrate may cause the loss of coating in the later stage of reaction. The cleaning of SiC particles with a NaOH or HF aq. solution suppressed the formation of agglomerates and increased the quantity of composite coating remarkably. It was suggested that the surface oxide layer of SiC particles is responsible for particle agglomeration. The agglomeration was not serious for coarse SiC particles with an average size of 1.1 or 5.8μm. However, when a plating solution was vigorously agitated, the quantity of composite coating decreased significantly with an increase in particle size. On the other hand, in moderate agitation, the quantity of composite coating was increased and the content of SiC codeposited showed a maximum at the particle size of 1.1μm.