Degradation and failure of a novel double-layer LC/YSZ thermal barrier coating in a burner rig corrosion test

Thermal barrier coatings (TBCs) are susceptible to corrosion by molten calcium-magnesium-aluminium-silicate (CMAS) during high temperature service. The microstructural evolution and thermal cycling lives of double-layer La₂Ce₂O₇ (LC)/yttria partially stabilised zirconia (YSZ) and single-layer YSZ coatings were comparatively studied by a burner rig corrosion test. The results suggest that the thermal cycling life of double-layer LC/YSZ coating is approximately 80% longer than that of single-layer YSZ counterpart. The CMAS penetrated into the whole YSZ coating, which remarkably accelerated the spallation failure of the coating. However, due to the superior CMAS resistance of the LC layer, the failure of the double-layer LC/YSZ coating was mainly caused by the sintering of the LC layer, which resulted in a large in-plane stress and initiation of cracks. These cracks propagated, branched and deflected along the LC/YSZ interface, ultimately leading to the spallation of the LC layer.