Abstract
Environmental barrier coating systems (EBCs) have been developed to protect SiC-based ceramics exposed to harsh environments. A series of novel EBCs containing 50HfO2-50SiO2 (molar ratio, 50HS) bond coat and YxYb(2−x)Si2O7 (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%H2O-10%O2 conditions, respectively. Monosilicate (Y/Yb)2SiO5 formed during the YxYb(2−x)Si2O7 deposition. The Re2O3-stabilized HfO2 solid solution with a high coefficient of thermal expansion formed at the YxYb(2−x)Si2O7/50HS interface due to the reaction between monosilicate (Y/Yb)2SiO5 and HfO2 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/YxYb(2−x)Si2O7 EBCs could effectively protect the SiC substrate at 1475 °C.
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