Atmospheric Plasma Spraying of High-Energy Ball-Milled Al₂O₃-TiO₂ Powders

Al₂O₃-TiO₂ materials are very attractive materials for the manufacturing of wear resistant ceramics coatings. Moreover, nanostructured coatings show superior properties (higher hardness and enhanced fracture toughness) as compared to their counterparts containing microscale grains. The aim of this study is to produce nanostructured Al₂O₃-TiO₂ coatings through the plasma spraying technique that can lead to metastable transformations. The starting powders containing 13wt% and 44wt% of titania, have been mechanically activated by high energy ball milling with a planetary mill, (Model P4 by Fritsch, Germany) using steel vials and balls in such conditions to obtained the high pressure TiO₂ II phase. The milled powders were then plasma sprayed with an Ar:H₂ gas mixture, by varying the plasma parameters (gas flow rates, nozzle diameter, aggregates size). The effect of the milling and the spraying conditions on the crystalline phases and the microhardness of the coatings are evaluated.