Effect of current density on the microstructure and properties of supercritical Ni-FG composite electrodeposited layers

Abstract

This study investigates the surface morphology and microstructure of nickel (Ni) plating and nickel-fluorinated graphene (Ni-FG) composite plating, both produced using a direct current (DC) power supply under standard and supercritical conditions. The findings reveal that the Ni-FG composite plating created under supercritical conditions can incorporate more fluorinated graphene (FG), with the carbon content reaching 0.727 wt%, surpassing the 0.155 wt% found in the plating produced by conventional electrodeposition. The supercritical plating also exhibits improved surface morphology, characterized by a smooth, defect-free surface. The grain size of the plating is notably smaller, averaging 7.39 nm, which is a reduction of over 59.6% compared to other plated layers, with grains predominantly oriented towards the (111) texture. The study focuses on comparing the surface morphology, microstructure, mechanical properties, and electrochemical characteristics of Ni-FG composite plating prepared at various current densities. Results indicate that at a current density of 5 A/dm2, the Ni-FG composite plating displays an exceptionally refined grain structure, with an average grain size of 7.39 nm. This plating layer exhibits excellent wear resistance, with a microhardness value of 772.2 HV0.2, a low coefficient of friction of 0.17, and a minimal wear volume of 1.890 × 107 μm3. Furthermore, the coatings produced at this current density exhibit exceptional corrosion resistance, as indicated by a film resistance (Rcoat) of 13,850 Ω cm2 and an interface resistance (Rct) of 10.96 × 104 Ω cm2 during the electrode oxidation process.

Keywords

• DC power supply
• Current density
• Supercritical Ni-FG composite plating
• Microstructure
• Properties