High-temperature oxidation performance of novel environmental barrier coating 50HfO2-50SiO2/YxYb(2−x)Si2O7 at 1475 °C

Environmental barrier coating systems (EBCs) have been developed to protect SiC-based ceramics exposed to harsh environments. A series of novel EBCs containing 50HfO 2 -50SiO 2 (molar ratio, 50HS) bond coat and Y x Yb (2-x) Si 2 O 7 ( x = 0.3, 0.5, 0.8, and 1.0) topcoat layers were deposited on SiC substrate using atmospheric plasma spraying in this work. Cyclic oxidation of EBCs was performed between room temperature and 1475 °C under dry air and 90%H 2 O-10%O 2 conditions, respectively. Monosilicate (Y/Yb) 2 SiO 5 formed during the Y x Yb (2-x) Si 2 O 7 deposition. The Re 2 O 3 -stabilized HfO 2 solid solution with a high coefficient of thermal expansion formed at the Y x Yb (2-x) Si 2 O 7 /50HS interface due to the reaction between monosilicate (Y/Yb) 2 SiO 5 and HfO 2 originating from the 50HS bond coat, which was detrimental to EBCs. Furthermore, the thermally grown oxide layer was found at the bond coat/SiC interface, and its formation mechanism has been studied. The results showed that the novel 50HS/Y x Yb (2-x) Si 2 O 7 EBCs could effectively protect the SiC substrate at 1475 °C.