Effect of electrodeposition parameters on the microstructure and properties of Cu-TiO2 nanocomposite coating

In the present research, Cu-TiO₂ nanocomposite coatings were prepared via pulse plating using a copper sulfate bath with 5 g/L TiO₂ nanoparticles; the process was undertaken on a steel substrate at room temperature for 60 min. Accordingly, the effects of process parameters such as duty cycle, pulse frequency, and average current density on the microstructure of the coating were investigated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis. Crystallite size and relative texture coefficient of the coatings were determined from X-ray diffraction (XRD) patterns. Also, microhardness and wear resistance of the coatings were measured using Vickers microhardness tester and pin-on-disk machine, respectively. Results showed that, the nanocomposite coating prepared at a duty cycle of 40%, frequency of 20 Hz and average current density of 2 A/dm² exhibited the highest microhardness with 1.98 wt% of TiO₂ content. Co-deposition of TiO₂ nanoparticles in copper coatings resulted in the modification of microstructure and variation in copper crystallite orientation, along with enhancements in microhardness and wear-resistances. The Cu-TiO₂ coating prepared under optimum conditions showed the copper crystallite size of 27 nm (40% smaller than the monolithic copper crystallite of pure copper coating) and microhardness of 180 HV (111% increase compared with pure copper coating). Also, the wear test results showed reductions in friction coefficient and wear rate as much as 33% and 50%, respectively, at the applied load of 3N compared with pure copper coating.