A comprehensive investigation of the effect of pulse plating parameters on the electrodeposition of Ni/ZrO2 composite coatings

Abstract

This study investigates the pulsed electrodeposition of Ni/ZrO2 composite coatings under different pulse frequency (f) and duty cycle (γ) values. It was found that these pulse conditions significantly influence the physicochemical phenomena at the cathode-electrolyte interface, which, in turn, impacts the electrocrystallization process of the electrodeposited metal. X-ray diffraction (XRD) analysis revealed that the crystalline orientation of the Ni/ZrO2 coatings varied with the applied f and γ values. Specifically, deposits made at f = 10 and 100 Hz with γ = 30% and 90% followed a [100] fibre texture, while coatings produced at f = 0.01 and 0.1 Hz under the same γ values exhibited a predominant [211] orientation. A mixed [100]+[200] orientation was observed in all other coatings. By adjusting the f and γ values, the mean crystallite size ranged from 19 to 33 nm. Energy-dispersive X-ray spectroscopy (EDS) results showed that the zirconia particle incorporation varied from 1.70% wt to 15.5% wt, depending on the pulsed current conditions. Coatings produced at lower f and γ values exhibited higher particle content, whereas those with γ = 90% showed the lowest incorporation rates. Scanning electron microscopy (SEM) images revealed a cauliflower-like morphology, with zirconia particles evenly distributed across the surface. Transmission electron microscopy (TEM) confirmed sub-micron particle clusters embedded in the metal matrix. Atomic force microscopy (AFM) analysis indicated an uneven topography with no surface defects. The surface roughness varied between Ra = 0.22 μm and Ra = 0.80 μm. Microhardness testing showed a significant increase in hardness, reaching a maximum of HV = 476 kp∙mm−2 under f = 10 Hz and γ = 70%.

Keywords

• Pulse electrodeposition
• Ni/ZrO2 composite coatings
• Electrocrystallization process
• Textural modifications
• Vickers microhardness