Sliding wear and electrochemical corrosion behavior of plasma sprayed nanocomposite Al2O3–13%TiO2 coatings

The conventional Metco 130 coating, densified nanostructured coating and undensified nanostructured coating were deposited by plasma spray. There were typical lamellar splats composed of columnar grains existed in the conventional Metco 130 coating. Whereas, the lamellar structures and columnar grains were not obvious in densified and undensified nanostructured coatings. The densified nanostructured coating had the highest sliding wear and corrosion resistance. Micro fracture, adhesive wear and tribochemical reaction occurred in all three coatings during their sidling against Si3N4 balls. The dominant wear mechanism in Metco 130 coating was micro fracture along splat and columnar grain boundaries. While, in nanostructured coatings the damage was intergranular fracture and grains pull-out. During the corrosion of densified nanostructured coating in 3.5%NaCl solution, the diffusion process of reactant through the coating was a determining factor. The NaCl solution could reach the steel substrate through permeable defects in coatings. The corrosion mainly occurred at the steel substrate near the NiCrAl bond coating/substrate interface.