Effect of current density and deposition time on microstructure and corrosion resistance of Ni-W/TiN nanocomposite coating

Abstract

Ni-W/TiN nanocomposite coatings were successfully prepared via pulse electroplating from an electrolyte containing suspended TiN nanoparticles. The effects of applied current density and deposition time on microstructure, morphology, composition, hardness and electrochemical behaviors of the obtained coatings were investigated. Results showed that the current density and deposition time affect remarkably the electrochemical co-deposition process and then the structure and characteristics of the composites. It illustrated that the nanocomposites are uniform, compact and crack-free. The nanocomposites prepared at Ia = 3 A dm−2 and t = 20 min had the finest structure, showing a fine and smooth surface. EDS mapping and XPS spectra illustrated that the TiN nanoparticles had been homogeneously dispersed throughout the coating. 2.34 wt% TiN nanoparticles were embedded in Ni–W (68.56 wt% Ni and 29.1 wt% W) alloy matrix at Ia= 3.0 A dm−2. The inclusion of TiN nanoparticles in Ni–W could promote the nucleation and cause a distinct microstructural change. The crystallite size was in the range of 11–15 nm. The average roughness value (Ra) is 65.7 nm and 73.8 nm for coating formed at 20 min and 40 min, respectively. The electrochemical measurements illustrated that Ia = 3–5 A dm−2 and t = 40–60 min was the optimal operating parameters for the excellent anti-corrosion properties of Ni–W/TiN nanocomposites. The embedded TiN in Ni–W matrix could fill defects then improve its corrosion resistance. This electrodeposited Ni–W/TiN nanocomposites possess excellent hardness and superior corrosion resistance, and is expected to be applied in aggressive environment as a protective coating.