Tribological and electrochemical corrosion behavior of Ni–W/BN (hexagonal) nano-composite coatings

Ni–W/BN (hexagonal) nanocomposite coatings were successfully electrodeposited on mild steel by direct current (DC) and pulse current (PC) methods. Electrodeposition was carried out by dispersing 2–8 g/l of BN (h) nanopowder into the nickel sulfate electrolytic bath. The coatings were characterized by Scanning electron microscopy (SEM), Energy dispersive analysis of X-Ray (EDAX), X-ray diffractometry (XRD), and Vicker׳s microhardness tester. Tafel polarization and electrochemical impedance methods were applied to measure the corrosion resistance properties of the nanocomposite coatings in 3.5% NaCl solution. Surface roughness and friction coefficient of the coated samples were assessed by Mitutoyo Surftest SJ-310 (ISO1997), and Scratch tester TR-101-M4. The tribological characteristics and corrosion resistance properties of the nanocomposite coatings were increased with the content of the BN (h) in the plating bath. Co-deposited BN (h) nano-particulates were uniformly distributed in the Ni–W alloy matrix. The Pulse current nanocomposite coatings have offered uniform surface, higher microhardness and excellent corrosion resistance properties than the DC composite coatings.