Recent progress in thermal/environmental barrier coatings and their corrosion resistance

Thermal/environmental barrier coatings (T/EBCs) play important roles in jet and/or gas turbine engines to protect the Ni-based superalloys and/or ceramic matrix composite substrates from the high-temperature airflow damage. Great efforts have been contributed to searching for enhanced T/EBC materials to improve the efficiency of the engines, which is the key of improving thrust-to-weight ratio and energy saving. The practical candidates, rare earth-contained materials, are widely used for T/EBCs in gas turbines due to their excellent properties such as low thermal conductivity, high melting point, high-temperature strength and durability as exhibited in yttria-stabilized zirconia, pyrochlore oxides and rare earth silicates. In addition to the intrinsic properties, the microstructures obtained by different synthesis processes and the service performances, as well as the underlying failure mechanism, are also significant to this specific application. However, the main challenges for T/EBCs developments are T/EBC materials selection with balanced properties and their anti-corrosion performances at higher operating temperature. In this review, we summarized the progress in their fabrication techniques and mechanical/thermal properties of typically rare earth-contained T/EBCs, together with their anti-corrosion performance under the condition of molten salts or oxides (such as, Na₂SO₄, V₂O₅ and NaVO₃), calcium–magnesium–alumina–silicate (CMAS) and high-temperature water vapor.