Improved Yttria-Stabilized Zirconia (YSZ) and Rare Earth Oxide (REO) Blends: Processability and Calcia–Magnesia–Alumina–Silicate Response

Author(s):

Clara Mock, Andrew Wright, Nickolas Sotiropoulos, Timothy Sharobem, Chris Dambra, Brian Keyes, and Anindya Ghoshal

Abstract:

There is a need for the development of tough, mechanically robust coatings resistant to calcia–magnesia–alumina–silicate (CMAS) glass attack for turboshaft gas turbine engine applications. Previously, an yttria-stabilized zirconia (YSZ) with gadolinium oxide (Gd₂O₃) composite coating was developed where the CMAS delaminated without infiltrating or forming reaction products. This coating was difficult to process due to poor flowability of the blended YSZ and Gd₂O₃ powders. A spray-drying and sintering route was used to develop readily processable YSZ rare-earth oxide (REO) mixed powders (where the REO was Gd₂O₃, samarium oxide [Sm₂O₃], cerium oxide [CeO₂], and hafnium oxide [HfO₂]) to further explore the effect of REO chemistry on CMAS behavior. Chemical reaction between the YSZ and REO formed a fluorite, (REO, Zr)O₂, phase for all mixtures except the YSZ–HfO₂ powder and coating. Characterization of the powders and air plasma spray coatings is included, as well as a discussion on the effect of REO chemistry on CMAS wettability behavior.