Plasma Sprayed Nanostructual Al₂O₃-13wt.%TiO₂ Coating

Recently advanced engineering ceramics such as Al₂O₃ and TiO₂ possess high hardness, high strength, chemical stability etc., which are widely studied and used. The Al₂O₃/TiO₂ ceramic coatings deposited by plasma spray also have been applied in many fields as surface coating to improve wear, fretting and corrosion resistance. Compared with conventional ceramic coatings, nanostructured ceramic coating has a more excellent performance, and thus drawn more attention.In this paper, ceramic Al₂O₃-TiO₂ system, as the subjects and carried out spray feed, the microstructure of powder and coatings were characterized by X-ray diffraction, scanning electron microscope. Their mechanical and wear performance were investigated, which were compared with those of the conventional counterpart. Obtained the following results:1. With nano-alumina and titanium dioxide as raw materials by spray-drying method, combined with high-temperature sintering technology, powders prepared by plasma spraying can be used for nanostructured Al₂O₃-13wt.% TiO₂ feedstock. Prepared by spray feed excellent performance with high bulk density, good mobility, the smaller particle size distribution.2. Using plasma spray technology to prepare nanostructured Al₂O₃-13wt.% TiO₂ coatings, alumina mainly containγ-Al₂O₃ phase, and a small amount ofα-Al₂O₃; did not find dioxide diffraction peak. Conventional coated with nanostructured coatings diffraction peaks similar to, but there is a small amount of Al2TiO5 phase.3. Nanostructured Al₂O₃-13wt.% TiO₂ coating has a unique "two-state distribution structure", that there is complete melting the structure, they tend to melt some of the structure. Nanostructured coating melt completely as part of the conventional coating structure is similar to the main lamellar structure.4. With the conventional Al₂O₃-13wt.% TiO₂ coating compared to the mechanical properties of nanostructured coating improved significantly. In the coatings prepared under different power, its micro-hardness with the increasing of power, nanostructured coating toughness than conventional coatings increased by 1/4.5. In the coating wear test, we found nanostructured Al₂O₃-13wt.% TiO₂ coating wear better than conventional coating, and the two kinds of coating wear different mechanisms.