Production and characterization of Ni-B/MgB2 composite coatings byelectroless deposition method

In this study, non-reinforced Ni-B and 0,1, 0,25 and 0,5g MgB2 particle-reinforced composite Ni-B coatings were produced by the electroless surface coating method on the AZ91 Magnesium alloy substrate materials, which is the most widely used magnesium alloy in industry and structural, mechanical, tribological, wettability and antibacterial properties of the produced coatings were investigated. The XRD results show that the Ni-B coating structure grown on the base substrate is amorphous and in the MgB2 particle reinforced coatings, crystalline MgB2O(OH)6, MgB2O5, MgO and MgB2xOy phases appear, causing a decrease in the peak intensity depending on the increase in the amount of particles. In morphological SEM analyses, it is seen that characteristic cauliflower Ni-B structure ends with initially local nucleation and then hexagonal MgB2 and its oxide structures with together MgB2 reinforcement. A decrease in hardness is seen, but raising in reinforcement amount causes an increase in hardness while the produced Ni-B coatings ensure a hardness higher than seven times. The higher friction values are obtained from the composite structures while Ni-B coating provides a decrease from 0,22 to 0,16 in terms of friction coefficient. The friction coefficients reduces from 0,8 to 0,5 depending on an increase in particle reinforcement. Wear ratios also vary in parallel. Wettability tests show that Ni-B coating structure exhibits a hydrophilic property and a clear transition to superhydrophilicity with MgB2 particle reinforcement realizes. Besides, in antibacterial tests, it is observed that MgB2 particle reinforced composite coatings are more antibacterial than Ni-B coatings and the best antibacterial property in the coatings produced is obtained in 0,1g - MgB2 particle reinforced coating.