Function of Reaction Layer in Pyrochlore Thermal Barrier Coatings against CMAS Corrosion

Higher working temperatures improves the energy conversion efficiency in gas turbine engines so thermal barrier coatings are applied to protect the blades to increase the operating temperature.  However, CaO-MgO-Al₂O₃-SiO₂ (CMAS) from volcanic ash and other debris can lead to corrosion of the coating. Rare earth zirconates with the pyrochlore structure are promising thermal barrier materials due to their low thermal conductivity and better corrosion resistance compared to the common thermal barrier material, yttria stabilized zirconia (YSZ). CMAS reacts with the pyrochlore materials to form cubic fluorite and silicate phases which can inhibit the corrosion process. In this presentation, Gd₂Zr₂O₇ and Sm₂Zr₂O₇ were used to study the corrosion mechanism of CMAS on pyrochlore materials.