The relationship between the film hole distribution and thermal cycle performance of TBCs by APS and HVOF

Thermal barrier coatings (TBCs) play an important role in protecting hot-end components of aero-engines from high-temperature oxidation and corrosion. The peeling of the TBCs around film holes has emerged as a major source of failure in thermal cycle oxidation. This study examines the failure behavior of TBCs on floating tiles in the combustion chamber of an aero-engine. Ninety thermal cycles were performed on two types of floating tiles with different film hole distribution. Results showed that the surface TBCs of sample No.1 peeled off by approximately 40 % of the total area, while 90 % of the surface TBCs of sample No.2 floating tile remained intact. A thermal cycling experiment of the TBCs on the surface of the floating tiles was performed to determine the stress distribution of the film holes by finite element (FE) simulation. The results indicated that there was a significant stress gradient on the TBCs surface around the film holes after thermal cycles, with 86.09 MPa and 62.84 MPa higher stress gradient around the film holes of sample No.1 floating tile compared to the film hole of sample No.2 floating tile on the surface and back side, respectively. This difference in the stress gradient and the film hole location on the TBCs led to spalling of the TBCs on the surface of both floating tiles. This study elucidates the failure mechanism of TBCs around film holes under thermal cycling through experiments and FE simulations, offering insights to improve the lifetime of TBCs.