Electroless deposition of nickel on the surface of silicon carbide/aluminum composites in alkaline bath

The aim of this work is improving the surface characteristics of aluminum matrix composites reinforced with 70 vol.% SiC particles (SiC_p/Al) used in relation to electroless Ni-P plating process in alkaline bath. Special pretreatment methods are necessary to obtain the films which have tight adhesion with the substrate, since the content of silicon carbide is higher than 70 vol.%. Palladium-free activation and palladium activation are successful in using to render the substrate surfaces auto-catalytically active towards metal deposition in the electroless solution, and furthermore, the sensitization step in the conventional process has been omitted. The structure, morphology and component of the coated layers are clarified by means of XRD, SEM and EDAX. Also, microhardness and adhesion measurements are carried out. The study indicates that the uniform Ni-P film is a mixture of microcrystalline and crystalline phases in the alkaline bath, with excellent adhesion to the substrate; the values of microhardness are enhanced after coating nickel.