On the Formation and Properties of Thermal Sprayed Al2O3 Coatings

In this work, the formation and properties of thermal sprayed Al₂O₃ coatings manufactured from experimental a&s powders are studied and discussed. Experimental powders were manufactured by spray drying of 40nm AlO(OH) and sintering the agglomerates at optimized temperatures in order to achieve γ-, δ-, θ- and α-Al₂O₃-powders. These powders were deposited with HVOF and APS systems. The aim was to characterize whether the phase structure of the powder influences the microstructure or properties of the deposited coatings. The microstructures of powders and coatings were characterized by SEM, TEM and XRD, mechanical properties by instrumented indentation and abrasive wear test, corrosion properties by dissolution tests and electrical properties by dielectric breakdown strength, resistivity, relative permittivity and loss index tests.