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

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.