Comparison of MWCNTs and GO reinforced electro-brush plated Ni nanocomposite coatings: structural variations of carbon-based reinforcements and tribological behavior

Abstract

Abstract As reinforcements, carbonaceous nanomaterials (CNMs) especially multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO), have attracted increasing attention in the application of electrodeposition. In this work, Ni-based nanocomposite coatings with MWCNTs and GO were prepared by electro-brush plating technique (EBP). The results showed that adding MWCNTs and adding GO both significantly improved the compactness of Ni coatings, however, the latter contributed more uniform microstructure and morphology of nanocomposite coatings owing to the excellent dispersion of GO. In addition, MWCNTs and GO could not only provide numerous nucleation sites for Ni primary crystals contributing the grain refinement, but also co-deposited with Ni atoms to form a strong interfacial bonding with Ni matrix. The addition of MWCNTs and GO can significantly reduce the worn volume of coatings from 7.52 × 107 μm3 to 3.49 × 107 μm3 and 2.82 × 107 μm3, respectively. Moreover, Ni nanocomposite coatings adding GO exhibited better wear resistance and friction stability than that of adding MWCNTs. Microstructural characterizations revealed that during wear testing, the agglomerated MWCNTs in nanocomposite coatings were destroyed severely and transformed into the shorten MWCNTs or the unfolded sidewalls, thereby leading to the instability of the wear process. In contrast, the damage degree of rGO was relatively slight. The nanosheets of rGO uniformly distributed in nanocomposite coatings became smaller and some of them were stacked between each other, which promoted the stability of friction process.