Abstract
Thermal barrier coating (TBC) systems, which have been inevitably introduced to the critical hot-section components such as blades and vanes of the advanced gas turbines, one required to assure the improved durability and reliability under the complicated modes of thermal-mechanical-chemical loadings. In the present paper, the stress rupture property evaluation and failure analysis were conducted for TBC system with the Y2O3 partially-stabilized ZrO2 top-coat in air and two kinds of the corrosive environments. Static creep loading was found to bring about the typical creep rupture behavior for TBC system similar to the no-coated Mar-M247 alloy in air regardless of aggressive environment. On the contrary, it was revealed that dynamic fatigue and creep-fatigue loadings tend to bring about a significant rupture life reduction of TBC system both in air and in corrosive environments, because the penetration crack pre-existing in the top-coat tends to provide a nucleation site for the fatigue crack in air, and the corrosion-fatigue crack in hot corrosive environment. In molten salt environment, furthermore, characteristic manner of crack propagation behavior was observed to occur such as crack branching and crack tip blunting, which should be rather effective for suppressing the crack propagation. Effect of the corrosive environments on such the crack behavior was discussed mainly from the viewpoint of dynamic fatigue crack propagation.
