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Black nickel coatings are widely used in industries due to their shiny black color and other unique properties. However these coatings are normally soft, which limits their applications. In order to increase the mechanical properties of black nickel coatings, sol-enhanced technology has been applied to the plating process. TiO2 sol-enhanced black nickel nanocomposite coatings were electroplated on nickel-coated brass. A systematic study on the microstructure and properties of the black coatings were conducted. The effects of TiO2 concentration (TiO2 sol concentration in 0-20 mL/L) on the surface morphology, nanohardness and wear resistance have been studied. The results indicated that the nanohardness of the sol-enhanced black nickel coating was increased by 20%. The mechanisms of improvement and surface morphology variation were also discussed. [ABSTRACT FROM AUTHOR]

Ni-Co-ZrO2 nanocomposite coatings have been electroplated on mild steel by adding ZrO2 nanoparticles into an Ni-Co plating solution. The microstructure and mechanical properties of nanocomposite coatings were systematically investigated. The results show that the microhardness of Ni-Co-ZrO2 nanocomposite coatings varied significantly with the quantity of ZrO2 nanoparticles. Ni-Co-10 g/L ZrO2 nanocomposite coating exhibited the optimum mechanical properties due to the dispersion strengthening effect. Addition of ZrO2 nanoparticles beyond 10 g/L led to particle agglomeration and caused a porous coating structure, resulting in a deterioration of coating mechanical properties. [ABSTRACT FROM AUTHOR]