Effect of Ni-Coated Multi-Walled Carbon Nanotubes on the Properties of Ni-B Composite Coatings on Aluminium Alloys

In this study, a Ni-B-NiMCNT composite was successfully coated onto the surface of a 7075 aluminium alloy using the electrodeposition technique. To investigate and identify the coating properties, we performed XRD(X-Ray Diffraction), SEM(scanning electron microscopy), EDS(energy-dispersive spectroscopy), microhardness testing, and friction wear testing. We discovered that the grain size of the plated layer decreases after the addition of NiMCNT. Also, the uniform distribution of Ni-coated MCNT fills the cracks and gaps in the hydrogen precipitation process and alters the coating morphology. These properties offer the composite coating and substrate interface a strong bonding force. Additionally, NiMCNT causes the growth of small nodules by inhibiting grain growth. An excellent composite layer can be obtained at a current density of 2.5 A/dm2, temperature of 45 celcius, rotational speed of 350 r/min, and NiMCNT concentration of 0.6 g/L. The hardness of the composite coating is 1265.4 HV, which is 41.2% higher than that of the Ni-B coating. Also, the minimum average friction coefficient is 0.4857, which is 16.6% lower than the Ni-B coating. We employed electrochemical methods to investigate the corrosion resistance of Ni-B-NiMCNT composite plating in 3.5 wt.% NaCl solution. Results indicated that the corrosion resistance of the plate is enhanced when the concentration of NiMCNT in the plating solution is 0.2 g/L.