A study on properties of electroless Ni-B/MgB2 coatings on AZ91 magnesium alloy

This study explores MgB₂ as a reinforcing agent in electroless deposition on AZ91 magnesium alloy substrates, evaluating its impact on coating properties. X-ray diffraction (XRD) analysis shows that the amorphous Ni-B coating masks initial magnesium peaks, while MgB₂ enhances MgB₂O(OH)₆, MgB₂O₅, MgO, and MgB_2xOy oxide phases. SEM images illustrate morphological shifts from cauliflower-like Ni-B structures to dendritic and fibrous MgB₂ forms, with higher MgB₂ concentrations leading to granular structures with randomly oriented crystallites resembling platelets, indicating increased magnesium content. MgB₂-reinforced Ni-B coatings exhibited higher hardness than the substrate but lower than as-deposited Ni-B. Friction coefficients initially decreased with Ni-B, increased significantly with 0.1 g MgB₂, and decreased with higher reinforcements, remaining higher than substrate and as-deposited Ni-B. MgB₂ reinforcement increased surface roughness, causing local agglomerations in 0.5 g MgB₂ coatings. Contact angle measurements demonstrated enhanced hydrophilicity due to MgB₂'s superhydrophilic properties influenced by surface roughness. Antibacterial tests revealed superior properties with 0.1 g MgB₂, suggesting a transition to MgB₂-enriched structures and influencing material properties. While Ni-B/MgB₂ coatings improved over substrate, further research is needed to optimize parameters and understand stabilizer effects. These coatings also exhibited superhydrophilicity and promising antibacterial properties, suggesting potential in advanced surface engineering applications.