Abstract
Atomic force microscopy was applied to study the formation and growth mechanism of thin multilayers of chromium-molybdenum and chrome prepared by electro-pulse plating, respectively. The chromium-molybdenum and chrome layers were prepared using direct current density of 1.6 mA.mm -2 and pulse currents with on-off time from 5 to 2000 ms in the bath containing 300g l-1 of chromic acid and 75g l-1 ammonium molybdate, and 250g l-1 of chromic acid and 5g l-1 of sulfuric acid, respectively. The higher current density enhanced nucleation rate which resulted in refining grain size. The micro-hardness of the pulse plated chrome and chromium-molybdenum alloy layers increased with the duration of on-off time and pulse current density. The average surface roughness of chrome layer is increased with increasing on/off time ratio for a given peak current density and voltage because the growth and dissolution mainly occurs during on-time and off-time, respectively. However, the average surface roughness of chromium-molybdenum alloy layer is decreased with increasing on/off time ratio for a given peak current density and voltage because the alloying element in the layer.
Published Version
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