Assessment of the Performance of Ni-Carbon Nanotube Nanocomposite Coatings for Protecting the Surfaces of Steel Agricultural Mower Knives

Abstract

In this study, nanotechnology is used to improve the wear and corrosion resistance of reciprocating mower knives. In particular, carbon nanotubes (CNTs) are used to reinforce the Ni-metal matrix, and the nanocomposite coating was obtained by electrodeposition on low-carbon steel (low-C steel). The effects of the CNTs concentration and current density on the surface morphology and the mechanical and chemical properties are investigated. Analysis of surface morphology reveals successful insertion of the CNTs in the Ni-metal matrix. Moreover, energy-dispersive x-ray spectroscopy (EDX) is used to verify successful co-deposition of the CNTs in the coating at 16 wt.% with operating parameters of 3 Adm−2 current density, 0.4 g L−1 CNTs concentration, and a pH level of 5. The Ni-CNTs nanocomposite shows high corrosion resistance compared with that of uncoated steel or pure Ni-coated steel. At 4.44 and 478.35 GPa, the nanoindentation hardness and Young’s modulus of the Ni-CNTs nanocomposite-coated steel are higher than those of pure Ni-coated steel, at 2.70 and 134.24 GPa, respectively. A fretting test of the Ni-CNTs nanocomposite coating reveals depth penetration of 308 nm, which is lower than that with pure Ni, at 938 nm. The major improvements in the mechanical properties of Ni-CNTs nanocomposite coatings are attributed mainly to a combination of dispersion and grain refinement effects.