Electrodeposition and Characterization of Ni-Al2O3 Nanocomposite Coatings on Steel

Monodispersed alumina particles were synthesized by the homogeneous precipitation under reflux boiling. The particles were employed as reinforcement additives in the electrodeposited Ni-Al₂O₃ composite coatings on steel. The deposited pure Ni and Ni-Al₂O₃ composite coatings were analyzed by SEM, XRD, and microhardness tester. The wear resistance and friction coefficient of the coated samples were determined by using a ball-on-disk tribometer. Furthermore, XRD analysis showed that coating temperature and the presence of particles in the deposited coatings had a noticeable effect on the preferred orientation of the crystalline faces of the nickel grains. Significant differences were noted in the texture coefficient of the pure Ni and Ni-Al₂O₃ composite coatings produced at different temperatures. These differences were attributed to the changes in the microstructure of the matrix caused by the embedded Al₂O₃ particles. Results revealed that wear resistance and the friction coefficient were turned out to be higher and smaller, respectively, for the composite coatings as compared to pure Ni coating at a given sliding distance. It was noted that the corrosion resistance of these specimens increased in the following order: bare substrate < pure Ni coating < Ni-Al₂O₃ nanocomposite coatings.