Novel thermal barrier coatings based on La2(Zr0.7Ce0.3)2O7/8YSZ double-ceramic-layer systems deposited by electron beam physical vapor deposition

Double-ceramic-layer (DCL) thermal barrier coatings (TBCs) of La2(Zr0.7Ce0.3)2O7 (LZ7C3) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single layer LZ7C3 coating, and even longer than that of the single layer YSZ coating. The superior sintering-resistance of LZ7C3 coating, the similar thermal expansion behaviors of YSZ interlayer with LZ7C3 coating and thermally grown oxide (TGO) layer, and the unique growth modes of columns within DCL coating are all very helpful to the prolongation of thermal cycling life of DCL coating. The failure of DCL coating is mainly a result of the reduction–oxidation of cerium oxide, the crack initiation, propagation and extension, the abnormal oxidation of bond coat, the degradation of t′-phase in YSZ coating and the outward diffusion of Cr alloying element into LZ7C3 coating.

Research highlights▶ LZ7C3 and YSZ have good chemical compatibility for the formation of DCL coating. ▶ DCL coating has a longer lifetime than that of single layer coating of LZ7C3 or YSZ. ▶ Similar TECs of LZ7C3 with YSZ coatings and YSZ coating with TGO layer. ▶ Unique growth modes of columns within DCL coating. ▶ Outward diffusion of Cr element (bond coat) into LZ7C3 layer.