2019 Volume 127 Issue 5 Pages 288-294
For the first time, Ni–ZrO2 nanocomposite coatings have been successfully co-electrodeposited by varying the concentration of ZrO2 particles in the bath. For this, to prevent agglomeration of ZrO2 nanoparticles in the plating bath and enhance the mass fraction of nano-particles in the composite coatings, the effects of surfactants and ZrO2 content on the Ni–ZrO2 nanocomposite coatings have been investigated. It was shown that the ZrO2 fraction and the microhardness of the composite coatings are improved by using less than 20 g L−1 ZrO2 and adding anionic and cationic surfactants, respectively. A high concentration of nanoparticles can cause agglomeration, which affects the Orowan strengthening effect. The addition of a cationic surfactant increases the charge on the ZrO2, migrates faster toward the cathode, and aids improvement of the ZrO2 nanoparticle fraction. In contrast, the anionic surfactant, due to its dispersion and ZrO2 fraction with a small increase, enhances the Orowan strengthening, which limits the plastic deformation of the coating and increases the improvement in coating hardness. Furthermore, the microhardness of the Ni–ZrO2 composite coating is further increased after a high-temperature annealing process up to a maximum temperature of 900°C, which results from the oxidation of nickel and the dispersion of ZrO2 nanoparticles.