Microstructure and tribological properties of nanostructured and conventional plasma sprayed alumina–titania coatings

• The grains of the nanostructured powder Al2O3–13TiO2 are produced from nanoparticles.
• The plasma sprayed nanostructured Al2O3–13TiO2 coating contains nanoparticles.
• The nanostructured Al2O3–13TiO2 coating possesses improved mechanical properties.
• The nanostructured Al2O3–13TiO2 coating possesses improved tribological properties.

The nanostructured and two conventional alumina–titania coatings were deposited by atmospheric plasma spray. The presented studies show that nanoparticles are the predominant component of nanostructured Al2O3–13TiO2 powder grains. The microstructure of coating consisted of two distinct regions: fully melted and unmelted or partially melted nanostructured areas, which were comprised of components of a starting powder. Microhardness and modulus of these coatings were significantly lower than the values obtained for nanostructured coating. It was found that the plasma-sprayed nanostructured Al2O3–13TiO2 coating possessed better tribological properties than those of conventional alumina–titania coatings. The lower coefficient of friction and wear of the nanostructured Al2O3–13TiO2 coating is attributed to the bimodal microstructure and the enhanced mechanical properties in comparison to conventional alumina–titania coatings.