Constrained sintering and thermal ageing behaviour of electrophoretically deposited Yb2Si2O7 environmental barrier coating

Abstract

The oxidation of SiC and the formation of a thermally grown oxide layer (TGO) limit the lifetime of environmental barrier coatings. Thus, this paper focuses on the deposition of denser Yb2Si2O7 coatings using electrophoretic deposition to reduce the TGO growth rate. The findings show densification for Yb2Si2O7 can be achieved with an optimized sintering profile (heating/cooling rate, temperature, and time). However, the addition of 1.5 wt. % of Al2O3 to Yb2Si2O7 promoted densification and lowered the required sintering temperature, at 1380 °C using 2 °C/min heating/cooling rate for 10 hours provided efficient coating density. Moreover, adding Al2O3 reduced the TGO growth rate by more than 70% compared to the Al2O3-free coatings, without cracking in TGO after 150 hours of thermal ageing at 1350 °C. Results within this study suggest electrophoretic deposition with Al2O3 addition produces promising Yb2Si2O7 environmental barrier coatings on SiC substrate with low oxidation rates and increased lifetime.