Root-like crack propagation: Synergistic of gradient structure and diffusion barrier in TBCs on TiAl Alloy

In this study, MYC (CoNiCrAlY-Y ₂ O ₃ -Cr ₃ C ₂ ) coatings and MYC/8YSZ gradient coatings were fabricated by atmospheric plasma spraying (APS) technology. During the oxidation cycle of the MYC coating, an in-situ diffusion barrier was formed at the interface between the coating and the substrate. The Vickers hardness test and nanoindentation experiments verified that this low-modulus, high-hardness diffusion barrier structure played the role of an "energy buffer layer". In the 900°C water quenching thermal shock test of the MYC/8YSZ gradient coating, after 960 cycles, it was found that the gradient structure extended the crack propagation path, improved the energy dissipation capacity of the coating, and formed root-like cracks inside the coating, which increased the thermal shock cycle life of the coating. The coating did not experience failure. This study demonstrated the advantages of gradient structures in improving coating performance, especially in terms of crack resistance under thermal shock conditions.