Altering the surface properties of the reinforcement elements in metal matrix composite materials

This present work is focused on studying to improve low wetting behaviour between liquid metal and ceramic particles. Ceramic particles such as silicon carbide (SiC) have attracted great attention because of their usability as reinforcement for composite materials. Autocatalytic (electroless) nickel deposition is an excellent process for the enhancement of surface properties of ceramic particles. However poor wettability of particles is one of the major drawbacks of metal matrix composite production. Various methods have been studied to enhance the wetting properties between ceramic materials and metal substrates during ceramic reinforced metal matrix composites. Among these methods autocatalytic nickel deposition is a unique process for the enhancement of the surface properties of ceramic particles. In this study, deposition of nickel–phosphorus (Ni-P) and nickel–boron (Ni-B) layer on SiC particles by way of autocatalytic plating in hypophosphite and borohydride baths was investigated. SiC powders were sensitised and activated respectively in order to ensure catalytic properties. Electroless nickel coating was performed from two different nickel ion sources (nickel chloride, nickel sulfate) following the pretreatments of particle surfaces. Coated powder morphologies were characterised by scanning electron microscopy. The results showed that a better uniformity and bonding were obtained for Ni-P coatings with the Ni2+ source of NiSO4.6H2O as compared to NiCl2.6H2O. For Ni-B coatings, the Ni2+ source of NiCl2.6H2O has provided better quality and continuous coating layer on SiC surfaces.