Achieving Superior Durability of Environmental Barrier Coatings through the Use of a Modified Silicon Bond Coat

The growth of a thermally grown oxide (TGO) layer has been identified as a major driving force for the failure of environmental barrier coatings (EBCs). It is always desirable to reduce the TGO growth rate in order to achieve a highly durable EBC system. In this study, an Al₂O₃-modified Si bond coat was developed for EBC applications. Both a Yb₂Si₂O₇/Si baseline EBC and a Yb₂Si₂O₇/(Si-Al₂O₃)-modified EBC were deposited using the air plasma spray process. The TGO growth behavior and cycling life of the EBCs were evaluated at 1316 °C in a 90% H₂O (g) + 10% air environment. The TGO growth rate in the baseline EBC is over four times faster than that of the modified EBC. The modified EBC survived 1000 cycles of steam testing without failure, while the baseline EBC has an average life of 576 cycles under identical conditions. The superior durability of the modified EBC can be attributed to the significantly reduced TGO growth rate.