Influence of electrodeposition parameters on the deposition rate and microhardness of nanocrystalline Ni coatings

In this paper, nanocrystalline nickel (nc-Ni) coatings were prepared by a direct current electrodeposition technique. Their microstructure and microhardness were investigated by a high-resolution transmission electron microscopy and a microhardness tester. It is found that the electrodeposition parameters, including content of C7H4NO3SNa∙2H2O, temperature and current density, have significant influences on the electrodeposition rate and microhardness of nc-Ni coatings. The electrodeposition rate increases with the current density stepwise. The largest electrodeposition rate is achieved at 60 °C. It decrease when the temperature is larger than 60 °C. The electrodeposition rate decreases with the increased content of C7H4NO3SNa∙2H2O. The microhardnesses of the nc-Ni coatings are higher on the condition of the larger current density, lower temperature or higher content of C7H4NO3SNa∙2H2O. But, it remains stable when the current density is in the range of 700–1000 A m− 2. The relationship between the mean grain sizes and microhardness fits for the Hall–Petch function, approximately.