Thermal durability and fracture behavior of layered Yb-Gd-Y-based thermal barrier coatings in thermal cyclic exposure

Abstract

The effects of structural design on the thermal durability of Yb-Gd-Y-based thermal barrier coatings (TBCs) were investigated through thermal cyclic exposure tests, such as furnace cyclic thermal fatigue (FCTF) and jet engine thermal shock (JETS) tests. The effects of composition in the bond coat and feedstock purity for the buffer layer on its lifetime performance were also examined. To overcome the drawbacks of Yb-Gd-Y material with poor thermal durability due to poor mechanical properties and low coefficient of thermal expansion, a buffer layer was introduced in the Yb-Gd-Y-based TBC systems. In the FCTF tests, the TBC with the CoNi-based bond coat and the buffer layer of regular purity showed a longer lifetime performance than other TBCs, especially the TBCs without the buffer layer.In the JETS tests, the TBC with the Ni-based bond coat and the buffer layer of high purity showed a sound condition after 2000 cycles, showing better interfacial stability for TBC with the Ni-based bond coat rather than that with the CoNi-based bond coat in the single layer coatings without the buffer layer. The buffer layer effectively enhanced the thermal durability in slow temperature change, while the bond-coat composition and the feedstock purity for the buffer layer were found to be important factor to improve the thermal durability of the TBC in fast temperature change. Finally, these research findings allow us to control the structure, composition, and feedstock purity in TBC system for improving the thermal durability in cyclic thermal environments.

Effect of thermal cycling frequency on the durability of Yb-Gd-Y-based thermal barrier coatings

“…where and are the CTEs of the top coat and the bond coat (CTE is 9-10 × 10 -6 K −1 for bulk YGYZ, 10.5-11.5 × 10 -6 K −1 for YSZ, and 15.0 × 10 -6 K −1 for metallic bond coat at 1000 °C [30][31][32]), respectively, the is the mean temperature in the top coat, and…”

Effects of Top Ceramic Layers with an Ultrathin Dense Layer on the Thermal–Physical Properties of Thermal Barrier Coatings

“…The partially yttrium-oxide-stabilized zirconia powder and coating have been previously prepared. 9.5Y 2 O 3 -5.6Yb 2 O 3 -5.2Gd 2 O 3 doped in ZrO 2 (YYG) was thought to have promising applications as a ceramic thermal barrier coating material in high-temperature environments due to its low thermal conductivity and high-temperature phase stability [24,25]. Its disadvantage is its poor thermal shock resistance.…”

ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3; a promising TBC material with high resistance to hot corrosion

“…Bahamirian et al [22] investigated the ZGYbY compound and reported that Yb-Gd-Y dopants in ZrO 2 promoted the formation of highly stable nontransformable (t´) zirconia phase. Also, Jung et al [29] examined the ZGYbY-based TBCs and showed that this compound possesses a considerable high-temperature sintering resistance introducing it as a coating with relatively high thermal barrier characteristics.…”