Bending Behavior and Microstructural Evaluation of YSZ TBC Deposited via SPS and SPPS for Advanced Turbine Applications

The efficiency and durability of gas turbines rely heavily on the performance of thermal barrier coatings (TBCs), which protect components from extreme temperatures and mechanical stresses. Yttria-Stabilized Zirconia (8YSZ) is well-established for its effectiveness in TBC applications, yet its mechanical behavior when deposited using emerging techniques like Suspension Plasma Spray (SPS) and Solution Precursor Plasma Spray (SPPS) remains underexplored, particularly in novel Inside-Out Ceramic Turbine (ICT) configurations. This work bridge that gap by examining the bending performance of 8YSZ coatings deposited via SPS and SPPS on titanium substrates, with a particular focus on microstructural control. Both dense and columnar microstructures were tailored through systematic manipulation of key process parameters, including plasma conditions, solvent composition, and feedstock concentration. The resulting microstructures were characterized in detail using SEM, XRD, and Raman spectroscopy. To simulate real-world operational conditions of the innovative turbine designs, a custom-designed four-point bending test was employed, subjecting the coatings to combined tensile and compressive stresses at elevated temperatures. This approach provided insights into the strain tolerance and delamination resistance of the TBCs. The study offers a comparative analysis of SPS and SPPS of 8YSZ and establishes a novel framework for assessing TBC performance under complex, application-specific stress conditions.