Abstract
The objective of this work is to study the cyclic oxidation performances of the environmental barrier coatings (EBCs) containing the novel HfO2-SiO2 bond coats in the air environment. Bi-layer HfO2-SiO2/Yb2Si2O7 (50HfO2-50SiO2, 70HfO2-30SiO2 bond coats) and conventional Si/Yb2Si2O7 EBCs were deposited on SiC substrate using atmospheric plasma spray. The effect of the pre-mixing ratios of HfO2/SiO2 on the cyclic oxidation behavior of HfO2-SiO2/Yb2Si2O7 EBCs was examined. The results showed that the higher content of the HfSiO4 formed from the 50HfO2-50SiO2 bond coats, and it remained intact. A thermally grown oxide (TGO) SiO2 layer was formed at the bond coat/SiC interface. The parabolic oxidation rate constant (kp, μm2/h) of the TGO has been reduced 2 orders of magnitude in 50HfO2-50SiO2/Yb2Si2O7 EBCs coated SiC compared to the bare SiC at 1475 °C, indicating that the 50HfO2-50SiO2/Yb2Si2O7 EBCs effectively protected the SiC substrate at 1475 °C.
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