Aspects of Al2O3-13% TiO2 Feedstock Powder Properties and Their Impact on the Microstructure and the Mechanical Properties of APS Coatings

For decades thermally sprayed coatings of Al₂O₃-13 wt.% TiO₂ have been applied in several commercial fields. Nevertheless, the influence of the detailed microstructural characteristics of the feedstock powders on the coating properties have been neglected so far. In this work we have systematically compared different commercial Al₂O₃-13 wt.% TiO₂ feedstock powders with varying aluminum titanate (Al₂TiO₅) contents and distinct distributions of the metallic elements. The impact of these feedstock powder properties on the microstructure and the mechanical properties of APS coatings was investigated at two different stand-off distances. Different from feedstock powders with higher TiO₂ contents, the existence of Al₂TiO₅ in the 13 wt.% TiO₂ powders resulted in an increased hardness in the APS coatings. Overall, the results point at the benefits of an enhanced homogeneity of the metallic elements in Al₂O₃-13 wt.% TiO₂ feedstock powders.