Electrocodeposition behavior of Ni-SiC composite under different shaped waveforms

In this paper, the electrocodeposition behavior of Ni-SiC was investigated under four different shaped waveforms which are rectangular, ramp-up, ramp-down and triangular waveforms with relaxation time. Experimental results showed that at the same peak current density, the rectangular waveform produced the largest amount of SiC embedded in the Ni matrix, whereas the other three waveforms had similar SiC content. A smaller grain size was observed in the deposit obtained by the rectangular waveform. The Guglielmi's model was extended to predict the volume fraction of SiC particles in the codeposition process using waveforms with arbitrary shape. The trend of the predicted volume fraction was found in good agreement with the experimental results. With the consideration of the influence of SiC particles on the free energy of creation of new interface and the growth of new grains, an analytical equation for average nucleation rates of the four waveforms was also derived. It was found that the highest nucleation rate was obtained for the rectangular waveform, which is in consistence with the experimental grain size as high nucleation rate is known to favor fine grains. (C) 2004 Elsevier B.V. All rights reserved.