Electrodeposition of Copper-Based Nickel–Graphene Coatings: Effect of Current Density on Microstructure and Properties

Nickel–graphene (Ni–Gr) coatings were synthesized on brass via electrodeposition to enhance the surface properties. The microstructure was characterized using SEM, XRD, EDS and Raman spectra, whilst microhardness, tribological behaviour, corrosion resistance and thermal conductivity were assessed. The results show that the current density during electrodeposition significantly influences the coating properties: at 2 A/dm2, the coating showed a dense structure, refined grains, and broad Ni diffraction peaks, with the graphene nanoplatelet uniformly distributed throughout. Under these conditions, the coating achieved optimal comprehensive properties: a Vickers hardness of 284 HV, the lowest average coefficient of friction (0.43) and minimal mass loss rate (2.01%) in friction and wear testing, and the highest corrosion resistance and the lowest self-corrosion current density (1.8135 × 10−6 A/cm2), with the thermal conductivity reaching its peak value (154 W/m·K, 25 °C). When the current density deviates from 2 A/dm2, nickel grain coarsening occurs, and the graphene nanoplatelet dispersion deteriorates, leading to reduced hardness, corrosion resistance, and thermal conductivity, whereas friction and wear intensify. Thus, 2 A/dm2 represents the optimum current density for electrodepositing copper-based Ni–Gr coatings, simultaneously optimizing the microstructure, mechanical properties, tribological performance, corrosion resistance and thermal conductivity. This study employs electrodeposition technology to provide a practical strategy for developing high-performance nickel-based coatings for copper-based heat sinks.