Thermal durability of thermal barrier coatings with bond coat composition in cyclic thermal exposure

• Thermal durability in TBCs with bond coat composition has been investigated.
• Cyclic thermal exposure tests were employed in determining thermal durability.
• The TBC with Ni-based bond coat showed a longer lifetime performance in both tests.
• Element Co easily creates the mixed oxide clusters during TGO growth.
• Ni-based bond coat showed a less hardness decrease than other bond coats after both tests.

The effects of bond coat composition on the microstructure evolution and thermal durability of thermal barrier coating (TBC) were investigated through cyclic thermal exposure. The microstructure of the bond coat was controlled using various feedstock powders, such as NiCrAlY, NiCoCrAlY, and CoNiCrAlY, which were coated on the Ni-based substrate using a high-velocity oxy-fuel process. The top coat was prepared with high purity feedstock powder (METCO 204 C-XCL) using an air plasma spray (APS) process. The thermal durability of the TBCs was evaluated through the cyclic thermal fatigue (CTF) and thermal shock (TS) tests, including the microstructure evolution, the thermally grown oxide (TGO) growth behavior, and thermomechanical properties. After the CTF and TS tests, the TBC with the Ni-based bond coat showed a longer lifetime performance and less degradation in hardness value than those with the Ni–Co- and Co–Ni-based bond coats. The results indicate that the bond coat composition produce an obvious effect on the thermomechanical properties of the TBC system. The relationship between bond coat composition and thermal durability is extensively discussed, based on the microstructure evolution and element diffusion behavior.