Production and properties of composite electroless Ni-B-SiC coatings

The study of electroless Ni-B coatings is pursued in order to obtain deposits on metal substrates with advanced properties such as high microhardness for particularly demanding engineering uses. In the present study, composite Ni-B coatings enhanced with SiC microparticles on a steel substrate were prepared using the method of electroless plating. Structure characterization was performed by means of X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) in order to draw conclusions concerning the dispersion and incorporation of SiC particles in the Ni-B matrix and how they affect surface roughness measured by a profilometer. Vickers microhardness tests were performed in order to demonstrate the notable increase in microhardness compared to the bare substrate. Furthermore, Tafel electrochemical tests in 3.5% NaCl(aq) were carried out in order to evaluate how the ceramic microparticles affect the behaviour of coatings in the corrosive medium. The results indicate, that improved deposits are obtained capable to withstand very demanding applications where high microhardness along with resistance to corrosion is a prerequisite.