Double-ceramic-layer thermal barrier coatings based on La_2(Zr_(0.7)Ce_(0.3))_2O_7/La_2Ce_2O_7 deposited by electron beam-physical vapor deposition

摘要

Double-ceramic-layer (DCL) thermal barrier coatings (TBCs) of La_2(Zr_(0.7)Ce_(0.3))_2O_7 (LZ7C3) and La_2Ce_2O_7 (LC) were deposited by electron beam-physical vapor deposition (EB-PVD). The composition, interdiffusion, surface and cross-sectional morphologies, cyclic oxidation behavior of DCL coating were studied. Energy dispersive spectroscopy and X-ray diffraction analyses indicate that both LZ7C3 and LC coatings are effectively fabricated by a single LZ7C3 ingot with properly controlling the deposition energy. The chemical compatibility of LC coating and thermally grown oxide (TGO) layer is unstable. LaAlO_3 is formed due to the chemical reaction between LC and Al_2O_3 which is the main composition of TGO layer. Additionally, the thermal cycling behavior of DCL coating is influenced by the interdiffusion of Zr and Ce between LZ7C3 and LC coatings. The failure of DCL coating is a result of the sintering of LZ7C3 coating surface, the chemical incompatibility of LC coating and TGO layer and the abnormal oxidation of bond coat. Since no single material that has been studied so far satisfies all the requirements for high temperature applications, DCL coating is an important development direction of TBCs.