Preparation of a dense ytterbium disilicate layer via dual electron beam physical vapor deposition at high temperature

Abstract

Ytterbium disilicate (Yb2Si2O7) is promising material for multilayered environmental barrier coatings (EBCs) on SiC fiber reinforced SiC matrix composites (SiC/SiC), because of its excellent volatilization resistance in a water vapor environment and the conformity of its coefficient of thermal expansion to SiC/SiC. A Yb2Si2O7 layer was formed on a mullite substrate, of which the combination was applied to the multilayered EBCs, via electron beam physical vapor deposition (EB-PVD) with dual electron guns using Yb2O3 and SiO2 ingots as vapor sources, simultaneously heating on the substrate at 1523K. The resulting layer consisted of a single-phase of Yb2Si2O7, with the (110) oriented structure. The layer had a highly dense columnar structure extending in the direction of thickness, but not the feather-like structure typical of layers synthesized via conventional EB-PVD techniques. It is expected that the application of dual EB-PVD during heating is useful for the construction of EBCs with excellent gas barrier performance.