Isothermal Oxidation Performance of High-Entropy Zirconate as an Advanced Topcoat for Thermal Barrier Coatings

High-entropy zirconates are a novel class of advanced materials that have been introduced recently as promising materials for topcoat applications in thermal barrier coatings (TBCs). High entropy zirconates have the potential to exhibit superior properties when compared to conventional yttria-stabilized zirconia (8YSZ) topcoats, which have a limited working temperature range of 1200-1300 °C. In this work, the isothermal oxidation behavior of high-entropy zirconate topcoats with a chemical composition of (Y_0.2Nd_0.2Gd_0.2Sm_0.2Dy_0.2)₂Zr₂O₇ has been studied. High entropy topcoats were thermally sprayed by suspension plasma spraying (SPS) on an HVOF-sprayed MCrAlY bond coat. By using the Mettech Axial III torch, the topcoats were produced with two distinct microstructures: columnar and dense vertically cracked (DVC). Oxidation tests were conducted at 5, 25, 50, and 100 hours at 1150°C to assess the performance of both microstructures in comparison to conventional 8YSZ topcoats. The development and growth of the thermally grown oxide (TGO) layer were studied to evaluate oxidation resistance and potential applications in high-temperature environments, such as gas turbine vanes, blades, and combustors.

Keywords: Thermal Spray, Suspension Plasma Spray, Thermal Barrier Coating, High entropy Zirconate, Oxidation