Investigating the Influence of Post-Heat Treatment on the Corrosion Resistance and Mechanical Properties of Nickel-Graphene Nanocomposite Coatings

This research aims to improve the mechanical characteristics of surfaces coated with nickel-graphene (Ni-G) nanocomposite material by using a single post-heat treatment surface hardening approach combined with oil quenching. The nanocomposite coating was developed using a pulse reverse electrodeposition technique using a Watts bath. The surface morphology of the coatings was analyzed with the help of X‑ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) with EDAX. The coated surface properties like micro-hardness, surface roughness, wear, and corrosion resistance were assessed by Vickers microhardness tester, roughness tester, pin-on-disk equipment, and electrochemical impedance spectroscopy. Specimens with Ni-G nanocomposite coating were post-heat treated at 400°C for 1 h, and oil quenched. With heat treatment, the coated surface exhibited superior properties in comparison with specimens that are not heat treated with a hardness of 467.3 HV, surface roughness of 0.638 µm, wear rate of  8.10 × 10^–7mm³/N m, and corrosion protection efficiency of 96.50%. The improved surface properties were due to the grain refinement and particle strengthening, with an increased average crystallite size of 19.6 to 23.82 nm, with a 75.59% reduction in average coefficient of friction achieved for the post-heat-treated surface than the bare surface.