Suspension High-Velocity Oxy-Fuel–Sprayed Dense Vertically Cracked and Suspension-Plasma-Sprayed Columnar Yttria-Stabilized Zirconia Coatings: Calcia Magnesia Alumino Silicates Infiltration and Thermal Cycling Performance

The quest to increase the surface temperatures and resistance to the corrosive environment of thermal barrier coatings topcoats mean that newer coating design strategies are needed. In this study, a performance evaluation of suspension high-velocity oxy-fuel (SHVOF)-sprayed dense vertically cracked (DVC) and suspension-plasma-sprayed (SPS) columnar structure (CS) topcoats is conducted. The calcia magnesia alumino silicate (CMAS) evaluation is conducted at 1300 °C for 30 min, whereas the furnace cycling tests (FCT) is conducted at 1135 °C for 45 min cycle dwell time. The CMAS infiltrates down to the bond coat layer, but does not induce partial or complete topcoat spallation on all studied topcoat layers. In terms of CMAS infiltration, the CMAS appears to be restricted along the vertical cracks. The FCT of the SPS CS structure indicates a failure largely at the thermally grown oxide (TGO)–topcoat interface, while the DVC topcoat layers indicate a mix-mode failure, i.e., both material-associated cracking and localized spallations at the TGO–topcoat interface. Overall, the SHVOF-sprayed ethanol-based DVC topcoat seems to offer a balanced trade-off, i.e., a majority of the topcoat is still intact after 100 thermal cycles and exceeds the material durability and performance offered by the SPS CS structure.