Plasma Spray-Physical Vapor Deposition Processing Effects on the Microstructure and Performance of Environmental Barrier Coatings

Plasma Spray- Physical Vapor Deposition (PS-PVD) is a hybrid technique bridges the gap between conventional thermal spray and vapor phase methods. PS-PVD can tailor microstructures and compositions to optimize coating characteristics. This process has been used in previous studies to deposit both thermal and environmental barrier coating materials. In the case of environmental barrier coatings, or EBCs, compositions have traditionally been rare earth silicates, which do not vaporize congruently via traditional vapor phase methods. In this work, the effect of PS-PVD processing conditions on a prospective EBC material (Yb₂Si₂O₇) were evaluated. Torch conditions, sample orientation, and powder feedstock were varied and samples were examined with X-ray diffraction and scanning electron microscopy for phase and microstructure evaluation, respectively. Selected materials were evaluated for performance under thermal cycling in a steam environment (90% H₂O/O₂) at 1426°C.