Influence of alumina nanoparticles on microstructure and properties of Ni-B composite coating

Influences of alumina nanoparticles on the microstructure and properties of Ni-B nanocomposite coating prepared by electro-co-deposition were studied. The effects of Al2O3 nanoparticles, current density and electrodeposition time on microstructure, corrosion resistance, hardness and surface electronic state of Ni-B nanocomposite coating were revealed by SEM, EDX, XRD, XPS and electrochemical methods. The results demonstrate that the inclusion of Al2O3 nanoparticles in Ni-B coating could improve the hardness and wear resistance accompanied with the grain refinement of the composite matrix. The incorporation of Al2O3 nanoparticles alters the crystal orientation and then the microstructure of the Ni-B matrix. This enhances the corrosion resistance of Ni-B/Al2O3 which is attributed to the compact structure and the reduction in the active surface area. XPS spectra indicate that the coating contains Ni, B, Al, N, O, and C. Under the influence of the grain refinement, hardening of the nanoparticles and the reduction in the active surface area, Ni-B/Al2O3 composite coating exhibits excellent corrosion resistance and hardness.