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

• Published in: Journal of the Ceramic Society of Japan Vol. 122; no. 1432; pp. 982 - 988
• Main Authors: KIM, Min-Sik, MYOUNG, Sang-Won, LU, Zhe, LEE, Je-Hyun, JUNG, Yeon-Gil, CHOI, Baek-Gyu, KIM, In-Su, CHO, Chang-Yong
• Format: Journal Article
• Language: Japanese
• Published: The Ceramic Society of Japan 2014
• Subjects: Air plasma spray; Bond coat; High velocity oxy-fuel spray; Layered structure; Thermal barrier coating; Thermal durability
• ISSN: 1882-0743; 1348-6535
• DOI: 10.2109/jcersj2.122.982

The effects of the bond coat structure on the microstructure evolution and lifetime performance of thermal barrier coatings (TBCs) were investigated through the cyclic thermal fatigue (CTE) and thermal-shock (TS) tests. The single layer and the first layer in the layered bond coat were prepared by high velocity oxy-fuel (HVOF) spray process using nickel-based feedstock. The second layer in the layered bond coat and the top coat were formed by air plasma spray (APS) process using nickel-based metallic feedstock and 8 wt % yttria-stabilized zirconia, respectively. The CTF tests were performed till 872 cycles with a dwell time of 60 min at a surface temperature of 1100°C and a bottom temperature of 950°C. Also, the TS tests were conducted until 300 cycles with a dwell time of 60 min at 1100°C. After the CTF and TS tests, the TBC system with the layered bond coat showed a better thermal durability than that with the single layer. The hardness value of the bond coat by HOVF process was dramatically decreased after the both tests, without much change in the bond coat by APS process. The diffusion trends of elements were similar with each other, less dependent on the bond coat structure, increasing amounts of cobalt and aluminum and decreasing those of nickel and tungsten. The microstructure evolution of the top coat, the growth behavior of thermally grown oxide layer, and the thermal durability were strongly affected by the thermal exposure condition and the bond coat structure.