Velocimetry of APS Spray of Rare Earth Disilicates for Environmental Barrier Coating Applications

This work uses in-flight particle dynamics to elucidate process-structure relationship of Atmospheric Plasma Spray (APS) rare earth disilicate (ReDS) coatings. APS ReDS are the state-of-the-art material for environmental barrier coatings (EBCs) top layer. Control of coating density, determined by the gaps and cracks of the APS lamellar microstructure, is required to achieve the desired for EBC performance.

YDS deposition by APS is well characterized and there is growing interest in alternative rate earth cations. The ability to apply YDS process understanding to other ReDS could significantly reduce resources for process development. We use plume particle dynamics, measured by dual slit velocimetry DPV-2000 (DPV), to explore process-particle dynamics relationships. DPV measures in-flight particles at the deposition plane providing a spatial map of in-flight particle flux, temperature, velocity, and particle size measurements. Microstructural imaging is employed to explore particle dynamics-structure relationship.

The effect of key process parameters and rare earth cation on in-flight particle dynamics 2. deposition rate, and 3. microstructure of APS of rare earth silicate EBCs is investigated. Three different rare earth compositions were deposited by APS. Process parameters are thermal spray torch current, gas flows, and torch to substrate distance.