Microstructure and properties of Al 2 O 3 –ZrO 2 –TiO 2 composite coatings prepared by plasma spraying

Abstract Al 2 O 3 –ZrO 2 –TiO 2 coatings were successfully prepared by plasma spraying Al 2 O 3 –ZrO 2 composite powders with and without TiO 2 addition. The effects of TiO 2 on the phase composition, microstructure and properties of the Al 2 O 3 –ZrO 2 coating were studied. The results show that the Al 2 O 3 –ZrO 2 –TiO 2 composite powder was composed of t‐ZrO 2 , α‐Al 2 O 3 , m‐ZrO 2 and rutile, while the Al 2 O 3 –ZrO 2 –TiO 2 composite coating consisted of t‐ZrO 2 , α‐Al 2 O 3 and γ‐Al 2 O 3 . The diffraction peaks of TiO 2 could not be detected in the Al 2 O 3 –ZrO 2 –TiO 2 coating even up to 10 wt% TiO 2 addition. The reason may be that TiO 2 was dissolved in the amorphous phase or formed solid solution with γ‐Al 2 O 3 phase in the coating during cooling. Compared with the Al 2 O 3 –ZrO 2 coating, the as‐prepared Al 2 O 3 –ZrO 2 –TiO 2 coating had denser microstructure, less microcracks and more amorphous phases. The density of the Al 2 O 3 –ZrO 2 –TiO 2 coating increased with the increase of TiO 2 content. The Al 2 O 3 –ZrO 2 –10wt%TiO 2 coating had the most uniform and dense microstructure, possessed higher toughness, adhesive strength and wear resistance compared with the Al 2 O 3 –ZrO 2 coating, which was due to its lower porosity and more uniform microstructure.