F. Hu

Effect of pulse frequency on electrodeposition behaviour of Ni–SiC composites

Abstract In the present paper, the effect of pulse frequency on electrodeposition behaviour of Ni–SiC composites was examined. Based on the impedance results of the composite, an equivalent circuit was used to describe the electrochemical system under different pulse frequencies. It was found that the simulated instantaneous peak current increased with decreasing pulse frequencies. A high peak current was known to favour nucleation and fine grain size. Experimental results revealed that the nickel grain size decreased with decreasing pulse frequency, and the volume fraction of SiC was relatively independent of pulse frequency. Microhardness and nanoindentation tests were also performed, and it was found that the hardness and the elastic modulus of the composite were dependent on the pulse frequency, and the phenomena could be explained by its change in grain size. The equivalent circuit was shown to be able to describe the coelectrodeposition system.

Effects of duty cycle on electrodeposition behaviour of Ni–SiCp composite coatings

Abstract Ni–SiCp composite coatings were synthesised by pulse electrocodeposition with different duty cycles. The grain size and the SiC particle content were found to increase with increasing duty cycle, and a maximum microhardness value was obtained at a duty cycle of 50%. Based on the results of electrochemical impedance spectroscopy, an equivalent circuit model was used to estimate the charge transfer current of the electrodeposition process at different duty cycles. The peak charge transfer current was found to decrease with increasing duty cycle. An analytical volume fraction equation was also applied to predict the content of embedded SiC particles in the composite coatings. The trend of the predictions was in consistent with the experimental results.