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.