Preparation and characterization of electroless Ni-B/nano-SiO2, Al2O3, TiO2 and CuO composite coatings

Ni-B/SiO2, Al2O3, TiO2 and CuO composite coatings were successfully obtained by the electroless plating technique. Dispersible SiO2, Al2O3, TiO2 and CuO nanoparticles were co-deposited with electroless Ni-B coating onto AISI-304 steel substrates. Deposits were characterized for its structural properties by X-ray diffraction (XRD). XRD results showed a broad peak of Ni-B and low intensity composite nanoparticle peaks. The surface and cross-section morphology of samples were analysed using a scanning electron microscope (SEM). Surface analysis showed that the incorporation in Ni-B matrix of nano-SiO2, Al2O3, TiO2 and CuO particles increases the nodularity of composite coatings. The deposits are composed of a columnar structure grown along the vertical direction of the substrate surface. The results also show that electroless nanocomposite coatings tend to have greater microhardness compared with the coating without nanoparticles. The increase in the microhardness of the nanocomposite coatings reported in this study is attributed to an effect of dispersion strengthening of ceramic particles in the Ni-B matrix.