Multifunctional electroless nickel boron composite coatings incorporated by magnesium diboride ceramic particles

Abstract

In this study, the role of MgB₂ in composite coatings is pivotal. Electroless Ni–B plating, a current-free chemical reduction process, deposits nickel–boron coatings. Other than MgB₂, reinforcements like SiC, B₄C, and so forth are used with Ni–B coatings for improved properties. The research focuses on Ni–B/MgB₂ coatings on AISI 4140 steel using electroless deposition and annealing at different temperatures. Initially, the coating appears dense and amorphous, transforming into worm-like structures through crystallization with MgB₂. Higher annealing temperatures lead to brush-like, feathery, and oyster mushroom structures, forming crystalline nickel boron compounds and oxide phases due to synergy. Interestingly, the newly introduced phases disrupt friction patterns nonlinearly, which is linked to MgB₂’s ceramic nature and reinforcement quantity. Conversely, incorporating MgB₂ and annealing-induced intermetallic phases notably enhances hardness (up to 6) and improves hydrophilicity and antibacterial traits in the coating.