Annealing behavior of Ni-TiO₂ nanocomposites

Ni-TiO₂ nanocomposite have been prepared by electrodeposition. The microstructure and tribological behavior of Ni-TiO₂ nanocomposite before and after annealing have been investigated compared with as-deposited Ni-TiO₂ composite. The results demonstrated that TiO₂ nanoparticles usually collected along the grain boundaries and nickel grains changed from columnar grains into equiaxed grains after annealing. HRTEM photographs indicated that the diffusion between crystalline nickel and TiO₂ nanoparticles did happen after annealing. Wear results indicated that the main wear mechanism of as-deposited Ni-TiO₂ nanocomposite was adhesion wear. The wear resistance of Ni-TiO₂ nanocomposite heat-treated is better than as-deposited Ni-TiO₂ nanocomposite because the oxidation layers on the worn surface of Ni-TiO₂ nanocomposite masked the strengthening effect of small grain size. The corrosion behavior also has been studied and it is found that annealing reduces the corrosion resistance of composite coatings.