Thermal barrier coatings of rare earth materials deposited by electron beam-physical vapor deposition

Thermal barrier coatings (TBCs) have very important applications in gas turbines for higher thermal efficiency and protection of components at high temperature. TBCs of rare earth materials such as lanthanum zirconate (La2Zr2O7, LZ), lanthanum cerate (La2Ce2O7, LC), lanthanum cerium zirconate (La2(Zr0.7Ce0.3)2O7, LZ7C3) were prepared by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, cross-sectional morphology and cyclic oxidation behavior of these coatings were studied. These coatings have partially deviated from their original compositions due to the different evaporation rates of oxides, and the deviation could be reduced by properly controlling the deposition condition. A double ceramic layer-thermal barrier coatings (DCL-TBCs) of LZ7C3 and LC could also be deposited with a single LZ7C3 ingot by properly controlling the deposition energy. LaAlO3 is formed due to the chemical reaction between LC and Al2O3 in the thermally grown oxide (TGO) layer. The failure of DCL-TBCs is a result of the sintering-induced of LZ7C3 coating and the chemical incompatibility of LC and TGO. Since no single material that has been studied so far satisfies all the requirements for high temperature applications, DCL-TBCs are an important development direction of TBCs.