Microstructure and properties of Al_(2)O_(3)-ZrO_(2)-TiO_(2)composite coatings prepared by plasma spraying

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),a-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),a-Al_(2)O_(3)and c-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 to10 wt%TiO_(2)addition.The reason may be that TiO_(2)was dissolved in the amorphous phase or formed solid solution with c-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)-10 wt%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.