Study on microstructure and friction behavior of nickel-graphene oxide coating by rare earth doped (Ni-GO/CeO₂) electrodeposition on titanium alloy

A specified amount of rare earth cerium oxide (CeO₂) and graphene oxide (GO) was incorporated into the Watts nickel plating solution to facilitate the preparation of a Ni-GO/CeO₂ plating on the TC4 titanium alloy substrate. The study focused on the influence of rare earth CeO₂ on the microstructure, grain size, microhardness, and friction and wear properties of the composite plating layer. The findings indicate that as the concentration of CeO₂ increases, the presence of holes and cracks in the plating layer significantly decreases. Notably, the imperfections in the plating layer were completely eliminated when the mass fraction of CeO₂ reached 3%. However, further increasing the CeO₂ content beyond 3% leads to the agglomeration of CeO₂ within the plating layer, which subsequently results in the reappearance of holes and cracks. XRD analysis and microhardness test results indicated that when the CeO₂ content was 3%, the composite plating exhibited the smallest Ni grain size at 42 nm, which is 28% smaller than that of the undoped CeO₂ layer. Correspondingly, the microhardness peaked at HV 384.84, marking a 15.83% increase compared to the undoped CeO₂ layer. However, with further CeO₂ doping beyond 3%, there was an increase in Ni grain size and a decrease in microhardness. The friction characteristics of the composite plating revealed optimal performance when the CeO₂ content was 3%. At this concentration, the friction coefficient reached its lowest value at 0.225, which is 24.24% lower than that of the undoped CeO₂ plating, with only slight abrasive wear observed. However, increasing the CeO₂ content beyond 3% led to a deterioration in the friction performance of the plating.