A Double Layer Thermal Barrier Concept made of Gadolinium Zirconate and YSZ

Partially yttria stabilized zirconia (YSZ) approaches limits of performance in long-term operation at 1200⁰C as a thermal barrier coating (TBC). For next generation of TBCs, higher temperature capability and longer lifetime of the coatings are essential to boost efficiency of gas turbine engines. In this work, gadolinium zirconate (Gd₂Zr₂O₇) (GZO)/YSZ double ceramic layer TBCs are presented enabling to withstand higher temperatures. Processing of the GZO layers by atmospheric plasma spraying with TriplexPro^TM spray torch, which is complicated due to the different vapour pressures of the feedstock constituents, is described taking advantage of particle diagnostics. Furthermore, influence of varied YSZ and GZO microstructures in terms of porosity on lifetime and failure modes of the double layers tested at 1400⁰C surface temperature is reported. Finally, properties of free-standing GZO layers with different microstructures and porosities such as Young`s modulus and sintering behaviour are discussed with regard to their impacts on TBC lifetimes.