Abstract
Air plasma sprayed thermal barrier coatings (APSed TBCs) exhibit splat microstructure formed by thin layers of lamellae (splats), and also include many interlamellar pores and voids. These microstructural features are primarily responsible for the low stiffness commonly exhibited by such coatings. The splat microstructure thus has an important influence on resistance to fractures, such as delamination, because thermal stress in coatings depends on its stiffness. Previous investigations have revealed that the mechanical properties of ceramic top coatings, such as stiffness and fracture toughness, vary not only with the thermal spray process but also with thermal exposure. In the present study, the correlation between the mechanical properties and splat microstructure of an APSed TBC is studied using the simple sintering model and numerical simulation (distinct element method). Numerical simulation results clarified that the mechanical properties of an APSed TBC were controlled by the splat microstructure, which varied depending on the sintering mechanism. The variation of mechanical properties in the APSed TBCs with thermal exposure can be predicted using the method proposed here.
