Impact Of Al2O3-TiO2 Feedstock Powder Characteristics On The Microstructure Of APS Coatings

Thermally sprayed coatings of Al₂O₃-TiO₂ are extensively used in commercial applications due to their favorable mechanical, electrical or thermal properties. Despite a long history of application, the detailed influence of the feedstock powder is still unclear. Especially, the effect of the compound aluminum titanate (Al₂TiO₅) on the formation and the properties of the coatings has only crudely been investigated. Accordingly, in this work we systematically examine the morphology, the elemental composition and the phase content of ten distinct commercially available feedstock powders of the common commercial compositions with 3, 13 and 40 wt. % TiO₂. Additionally, Al₂O₃ and TiO₂ powders are used for comparison. Subsequently, the powder characteristics are related to the resulting microstructure and the properties of Al₂O₃-TiO₂ APS-sprayed coatings, with a special focus on the role of the Al₂TiO₅. Thereby, improved coating properties can be expected by specifically tailoring the phase composition within the Al₂O₃-TiO₂ coating via an improved specification of the feedstock powder.