Gradient thermal cyclic behaviour of La2Zr2O7/YSZ DCL-TBCs with equivalent thermal insulation performance

Thermal insulation performance is a measure of the thermal protection function offered by the thermal barrier coatings (TBCs) to the substrate. In this study, a series of La2Zr2O7 (LZO)/YSZ DCL-TBCs, with the equivalent thermal insulation to 500 mu m thick YSZ TBCs were prepared, and their lifetimes were evaluated by thermal gradient cyclic test at the top coat surface temperature of 1300 degrees C. Results show that, the lifetime of DCL-TBCs was more than doubled compared to 500 pm thick YSZ TBCs, when 100 mu m and 200 mu m thick YSZ coating was substituted by LZO coating. With the increase of LZO substitutional ratio, the delamination position transferred from near top/bond coating interface to near the LZO/YSZ interface and finally to the inside of the LZO coating. The porosity and elastic modulus present a differential distribution across the thickness of top coat. This study provides some data for the composite structure design of next generation advanced DCL-TBCs.