Study on wear and corrosion properties of functionally graded nickel-cobalt-(Al2O3) coatings produced by pulse electrodeposition

摘要

Functionally graded nickel-cobalt coatings with/without alumina nanoparticles were pulse electrodeposited on a carbon steel substrate by a continuous decrease in duty cycle from 95 to 10% at different frequencies of 100, 500 and 1000 Hz. The effect of pulse parameters on the nanoparticle content, chemical composition, microstructure, corrosion properties and tribological behaviour of coatings was studied. Energy-dispersive X-ray spectroscopy analysis showed that the amount of cobalt is gradually reduced and the content of alumina nanoparticles is increased from the substrate/coating interface to the surface. Based on the electrochemical studies in 3.5 wt% NaCl, the nanocomposite coatings gain the highest corrosion resistance at the lowest frequency. Also, the hardness of coatings gradually increased. Evaluation of the tribological behaviour of coatings by a pin-on-disk wear test showed that the nanoparticles have a positive effect on wear resistance and improve it by increasing frequency.