Microstructural, mechanical and tribological characteristics of reduced graphene oxide (rGO) reinforced nanostructured Al₂O₃-13wt. %TiO₂ coatings

Al₂O₃-13wt. %TiO₂ is a widely used coating material for the protection of metallic surfaces. The reduced graphene oxide (rGO) added alumina-titania composite coatings deposited using Air Plasma Spraying (APS) are used for enhancing the wear resistance of engineering components. In this work, the addition of rGO at varying weight percentages of 0.5, 1, and 1.5% to the Al₂O₃-13wt.%TiO₂ powder resulted in composite coatings with improved microstructural characteristics, mechanical properties, and tribological performance. The use of SEM and XRD analyses revealed the presence of rGO between the coating splats, offering protection from crack initiation. Furthermore, there were noticeable changes in the microhardness and surface roughness of the coatings. Coatings reinforced with higher weight percentages of rGO had extremely low wear rates and offered a low coefficient of friction, with unpulled rGO acting as protective layers. However, it was also observed that the wear of coatings with 0.5 wt% and 1.0 wt% rGO addition was mainly due to the delimitation and subsequent pulverization at 1.5 kgf load and 0.17 m/s sliding speed. Overall, this work provides valuable insights into the use of composite coatings for enhancing the wear resistance of surfaces of components.