Structural, morphological and mechanical properties of electroless Ni-B based alloy coatings

The electroless Ni-B alloy coatings are prepared using an alkaline plating bath with nickel chloride as the source of nickel ions and sodium borohydride as the reducing agent as well as the source of boron ions in presence of zinc acetate in the plating bath. The effect zinc acetate concentration on plating rate, chemical composition, surface morphology, structural characteristics, hardness and wear properties of the electroless Ni-B alloy coatings are evaluated. The boron content in the Ni-B alloy coating decreased from 3.69 wt % to 3.26 wt%, when the zinc acetate concentration increased from 1 g/l to 4 g/l in the electroless plating bath. The scanning electron microscopic observation revealed formation of corn-cob like structure on the coating surface. The X-ray diffraction analysis confirmed the crystalline nature of the Ni-B alloy coatings. The microhardness values of the Ni-B alloy coatings decreased from 650 HV to 507 HV, when zinc acetate concentration in the plating bath increased from 1 g/l to 4 g/l. (C) 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International conference on Materials and Manufacturing Methods.