MICROSTRUCTURAL EVOLUTION IN PULSE PLATED NICKEL ELECTRODEPOSITS

Square-wave cathodic current modulation was used to electrodeposit ult rst-fine-grained nickel from an additive-free Watts bath. The influenc e of pulse parameters, namely, pulse on-time, off-time and peak curren t density on the grain size, surface morphology and crystal orientatio n was determined. The study showed that an increase in peak current de nsity resulted in considerable refinement in crystal size of the depos it. The crystal orientation progressively changed from an almost rando m distribution at the lowest peak current density of 400 mA cm(-2) to a strong (200) texture at a peak current density of 1600 mA cm(-2). At constant peak current density and off-time, the crystal size of the d eposit was found initially to decrease with pulse on-time before it st arted to increase with further increase in on-time. The crystal orient ation progressively changed from an almost random distribution at the shortest on-time of 1 ms to a strong (200) fibre texture at an on-time of 8 ms. An increase in the pulse off-time at constant on-time and pe ak current density resulted in a progressive increase in crystal size. However, the crystal orientation remained unaffected with increasing off-time.