A comparative study of electrodeposition techniques on the microstructure and property of nanocrystalline cobalt deposit

Nanocrystalline Cobalt (Co) deposits with different microstructures are produced by direct current (DC), unipolar pulse, reverse pulse, and bipolar pulse electrodeposition processes. The microstructural characteristics of the resulting deposits, including average grain size, phase structure, surface roughness and morphology, are greatly affected by the electrodeposition techniques used. The hardness, friction and wear behaviors, and the electrochemical corrosion properties of the deposit are strongly dependent on the microstructural characteristics. The bipolar pulse electrodeposition produces nanocrystalline Co deposit that is featured by small grain size and low surface roughness, and consequently the highest hardness and resistances to wear and corrosion. The nanocrystalline Co deposit produced by the reverse pulse electrodeposition exhibits the smallest grain size and highest hardness but the lowest wear resistance attributable to its rough surface and indistinctive hcp (100) and (110) textures. DC plating has produced Co deposit with the largest grain size, the lowest hardness and corrosion resistance, and a relatively low wear resistance. The electrodeposition mechanisms involved in these processes are explained and related to the microstructures, properties and wear mechanisms of the resulting nanocrystalline Co deposits.