Tribological properties of pulse plated nanocrystalline nickel coatings as environmentally accepted alternative to conventional chromium coatings

摘要

In this study, the tribological properties of nanocrystalline nickel coatings were compared with those of conventional hard chromium coatings. Nanocrystalline nickel coatings were synthesised in a Watt's bath using the pulse electroplating technique. Changes in the saccharin concentration in the Watt's bath were studied in order to develop superior properties for nanocrystalline nickel coatings relative to conventional chromium coatings which were electroplated galvanostatically. Wear resistance, microhardness, surface roughness and coefficient of friction were evaluated for both electrodeposits. Tribosurfaces were studied by scanning electron microscopy and energy dispersive X-ray analysis. X-ray diffraction patterns were used to determine the average grain size of nanocrystalline nickel coatings. Nanocrystalline nickel coatings (10 nm grain size) showed higher microhardness values than chromium coatings. Also, high saccharin concentration in the nickel bath resulted in nanocrystalline nickel coatings with higher wear resistance, lower coefficient of friction, lower surface roughness and brighter appearance than chromium coatings.