Hybrid chemical-physical vapor deposition of highly durable environmental barrier coatings

Abstract

Environmental barrier coatings (EBCs) are needed to protect SiC based ceramic matrix composites (CMCs) from steam attack in next generation aircraft engines. In this study, EBCs consisting of a dense Yb2Si2O7 top coat and a columnar structure silicon bond coat were deposited using a hybrid chemical-physical vapor deposition process. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the coating phase composition and microstructure. The as-deposited Yb-Si-O coating is highly amorphous, and it transformed to crystalline Yb2Si2O7 and Yb2SiO5 phases after 1300 °C heat treatment in air. The durability of Yb2Si2O7/Si EBC was evaluated in a steam cycling test in flowing 90% H2O (g) + 10% air at 1316 °C, and the EBC survived 1000 1-h steam cycles without failure, which demonstrated the excellent durability of the hybrid vapor deposited Yb2Si2O7/Si EBC.