Hot corrosion behavior of double-ceramic-layer LaTi ₂Al ₉O ₁₉/YSZ thermal barrier coatings

LaTi ₂Al ₉O ₁₉ (LTA) exhibits promising potential as a new kind of thermal barrier coating (TBC) material, due to its excellent high-temperature capability and low thermal conductivity. In this paper, LTA/yttria stabilized zirconia (YSZ) TBCs are produced by atmospheric plasma spraying. Hot corrosion behavior and the related failure mechanism of the coating are investigated. Decomposition of LTA does not occur even after 1 458 hot corrosion cycles at 1 373 K, revealing good chemical stability in molten salt of Na ₂SO ₄ and NaCl. However, the molten salt infiltrates to the bond coat, causing dissolving of the thermally grown oxide (TGO) in the molten salt and hot corrosion of the bond coat. As a result, cracking of the TBC occurs within the oxide layer. In conclusion, the ceramic materials LTA and YSZ reveal good chemical stability in molten salts of Na ₂SO ₄ and NaCl, and the bond coat plays a significant role in providing protection for the component against hot corrosion in the LTA/YSZ TBCs. LTA exhibits very promising potential as a novel TBC material.