Investigation of Ni-Cu-B and Ni-Cu-Sn-B coatings developed by electroless method

Abstract

Due to their remarkable mechanical properties and tribological behaviour which is equivalent the hard chrome coating, electroless Nickel–Boron coatings have been employed in a variety of industries. With the advent of emerging and challenging applications, there has been a need to develop newer variants of the novel Ni-B binary variant. The present work therefore investigates Ni-B-Cu coatings in a quest to achieve higher wear and corrosion resistance. A stabilizer free bath and tin chloride stabilized bath was formulated for the same to remove the harmful lead nitrate from the coating formulation. The concentration of copper sulphate was varied from 0.3 to 0.7 g/L in both the bath formulations. Based on the mass gain of the specimens, coatings obtained from 0.6 g/L copper sulphate was further investigated. The surface morphology of as-plated samples was observed which shows nodular structure and the growth was different compared to lead stabilized baths. The constant load and progressive scratch test were done to evaluate scratch hardness and coating failure respectively.