Influence of spike current in different shaped waveforms on the hardness and grain size of nickel electroforms

This paper studies experimentally and theoretically the effects of a ramp-d own spike-shaped waveform. on the grain size and the hardness of nickel ele ctroforms in pulse current electroforming. Experimental results show that t he quality of the electroforms, in terms of hardness improvement, influence d by the types of waveform is in the order of: ramp-down and triangular, bo th with spike > rectangular with spike > ramp-down; and triangular, both wi th relaxation time > rectangular. Compared with the results for the convent ional rectangular waveform, the experimental results show that the hardness value can be improved by about 46% when a ramp-down spike and a relaxation time are used in the case of triangular or ramp-down waveform. The finest grain size and the highest hardness value were obtained by using a ramp-dow n spike in either triangular or ramp-down waveform. These results are suppo rted by theoretical predictions and study of the surface morphology of the electroforms using a scanning electron microscope. (C) 2001 Elsevier Scienc e B.V. All rights reserved.