Study of the microstructure of plasma sprayed coatings obtained from Al2O3–13TiO2 nanostructured and conventional powders

• Plasma sprayed Al2O3–13TiO2 coatings reveal diversity of microstructure.
• Microstructure of conventional coating was formed from fully melted crushed powders.
• Nanostructured coating contains completely and partially melted initial agglomerates.

The microstructure of coatings obtained from nanostructured or conventional Al2O3–13TiO2 powders and deposited by plasma spraying technique on low-carbon steel was examined by transmission electron microscopy techniques. The dominating phase in both coatings was γ-Al2O3 phase. It has been observed that the grains of γ-Al2O3 grew in various shapes and sizes, that are particularly visible in the case of coating sprayed from nanostructured powder. The coatings obtained from the fully melted conventional powders exhibited a typical lamellar microstructure, into which the strips of TiO2 phase were extended. The microstructure of coatings produced from agglomerates of nanostructured particles also revealed the regions consisting of partially melted α-Al2O3 powders surrounded by the net-like structure formed from fully melted oxides that improved the coating properties. Along with the observed morphology diversity some changes in the chemical composition on the cross sections of obtained coatings have been also noticed.