Electrodeposition and mechanical property of Ni–Co–ZrC coatings

Abstract

In order to improve the mechanical properties of Ni–Co coating, Ni–Co–ZrC composite coatings were electrodeposited from a modified Watts bath. Surface morphology, composition and microstructure of the coatings were characterised by scanning electron microscopy, energy dispersive spectrometer and X-ray diffraction analysis. Mechanical properties of the coatings including microhardness and tribological behaviour were investigated by Vicker microhardness tester and tribotester. Ni–Co and Ni–Co–ZrC coatings all exhibited anomalous deposition behaviour. By increasing the Co content, surface morphology of the coatings was changed from nodular structure to branched morphology and the dominant phase was changed from fcc Ni to hcp Co. Compared with Ni–Co coatings, Ni–Co–ZrC coatings possessed smaller grain size and exhibited better mechanical properties. Phase composition, grain size and ZrC particles content of the coatings were applied to explain the evolution of the morphology, microstructure and mechanical properties of the coatings. Among the coatings, Ni-Co-ZrC coating with 43 at-% Co exhibits the highest microhardness and the Ni-Co-ZrC coating with the highest Co content exhibits the best tribological behaviour.