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 center dot 2H(2)O, 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 degrees C. It decrease when the temperature is larger than 60 degrees C. The electrodeposition rate decreases with the increased content of C7H4NO3SNa center dot 2H(2)O. The microhardnesses of the nc-Ni coatings are higher on the condition of the larger current density, lower temperature or higher content of C7H4NO3SNa center dot 2H(2)O. 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. (C) 2009 Elsevier B.V. All rights reserved.