Tribological behaviour of nanostructured Al2O3-3wt% TiO2 coating against steel in dry sliding

Nanostructured and conventional Al2O3-3wt% TiO2 coatings were deposited by atmospheric plasma spraying. The wear and friction properties of both coatings against a steel ball under dry friction conditions were examined. It was found that the wear resistance of the nanostructured Al2O3-3wt% TiO2 coating was superior to that of the corresponding conventional counterpart. The improvement in wear resistance of the nanostructured coating was attributed to its higher toughness and cohesion strength between splats. As for the nanostructured coating, the wear mechanism was mainly adhesion with micro-abrasion at low loads (20 N). At high loads (80 N), the wear of the nanostructured coating was controlled by plastic deformation and associated delamination along the splat boundaries, which was similar to that of the conventional coating at low loads. However, the failure of the conventional coating was predominantly brittle fracture within the splats and delamination between splats at high loads.