Microstructure and mechanical properties of plasma sprayed alumina-based coatings

Abstract Alumina-based coatings are employed in many industrial applications, in order to protect the surface of metal components against high temperature, wear, corrosion and erosion. In this work two different alumina-based coatings were fabricated by atmospheric plasma spraying (APS), starting from powder particles composed of pure Al 2 O 3 and Al 2 O 3 -3 wt% TiO 2 , respectively. Their phase composition was investigated by X-Ray Diffraction (XRD) and revealed that both the as-sprayed coatings were mainly composed of metastable γ- and α-Al 2 O 3 phases. The γ phase recrystallized to α phase after heat treatment. The porous microstructure was analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Thin TiO 2 -rich splats were observed within the microstructure of alumina–titania coatings. The pure alumina coatings exhibited similar porosity and higher microhardness than the alumina–titania ones (12.8 against 9.9 GPa). Both the coatings herein analyzed are particularly promising for high-temperature anti-wear applications, because of their enhanced mechanical properties.