Tribological Electroless Ternary Ni-B-W Coatings: A Suitable Alternative to Hard Chromium Coatings

Abstract

Concerns raised about the environmental ramifications of electrodeposited hard chromium (EHC) plating are perhaps the paramount challenge posed to the finishing industries to find a suitable alternative. Electroless Ni-B coatings have attracted much attention due to their superior mechanical and tribological properties; those are enhanced further in electroless Ni-B-W coatings. Electroless Ni-B-W can be a suitable alternative for the replacement of EHC in variety of engineering applications. In the present study, the changes in morphological features, deposition rates with respect to time, and deposition mechanisms of electroless Ni-B-W coatings are studied thoroughly. After heat treatment, all deposited coatings are characterized thoroughly for the evaluation of their mechanical and tribological characteristics. This is helpful in the comparison of characteristics with properties of industrial EHC coatings. To analyze the coating-substrate adhesion in the electroless depositions, scratch tests with progressive load and repetitions are carried out. Frictional behavior and failure mechanisms at the scratch tracks of all fabricated coatings are also studied through repetitive scratch tests. Heat treatment of electroless Ni-B-W coatings induced significant improvements in mechanical properties, tribological properties, and adhesion behavior. The present study establishes beyond doubt that owing to a specific set of properties, electroless Ni-B-W coatings show tremendous potential to be recommended as a replacement for chrome coatings.