Synthesis and characterization of Ni– $$\hbox {Si}_{3}\hbox {N}_{4}$$ Si 3 N 4 nanocomposite coatings fabricated by pulse electrodeposition

Abstract

Pure Ni and Ni–silicon nitride $$(\hbox {Si}_{3}\hbox {N}_{4})$$ nanocomposite coatings have been successfully fabricated on copper substrates by a pulse electrodeposition method employing the Watts bath. The obtained coatings were characterized with X-ray diffractometry and scanning electron microscopy. Also, surface hardness and the corrosion behaviour of the coatings were analysed by potentiodynamic polarization and electrochemical impedance spectroscopy in a 3.5% NaCl solution. It was found that incorporation of $$\hbox {Si}_{3}\hbox {N}_{4}$$ particulates has reduced the crystallite size and also changed the growth orientation of the crystallite from (111) to (220) and (200) crystal planes. The co-deposition of $$\hbox {Si}_{3}\hbox {N}_{4}$$ in the Ni matrix led to better properties of these coatings. Accordingly, the hardness value of nanocomposite coatings was about 80–140 Hv higher than that of pure nickel due to dispersion-strengthening and matrix grain refining and increased with the enhancement of incorporating $$\hbox {Si}_{3}\hbox {N}_{4}$$ particle content. The presence of the $$\hbox {Si}_{3}\hbox {N}_{4}$$ particulates slightly decreases the current efficiency. The current efficiency was decreased by increasing current density from 1 to 4 A $$\hbox {dm}^{-2}$$ . Moreover, the corrosion resistance of nanocomposite coatings was significantly higher than the pure Ni deposit. Also, the Ni– $$\hbox {Si}_{3}\hbox {N}_{4}$$ coating produced at a density of 4 A $$\hbox {dm}^{-2}$$ showed the lowest corrosion rate (0.05 mpy).