Thermal stability and thermal cycling behavior of LGYYSZ/YSZ thermal barrier coatings fabricated by atmospheric plasma spraying

Double ceramic layer (DCL) represents an efficacious approach to reinforce the high-temperature durability of thermal barrier coatings (TBCs), but research on the influence of intermediate ceramic (IC) thickness on coating failure mode lacks systematic research. In this study, 1.0La-2.0Gd-2.0Yb-4.5Y-ZrO2 coatings with three YSZ IC of different thicknesses (LGYYSZ/YSZ) were prepared via atmospheric plasma spraying (APS). A comprehensive investigation was conducted on the thermal cycling performance of the spray-as-deposited TBCs at 1400 degrees C. The results indicated that the incorporation of YSZ IC significantly enhances the stress resilience at the TC/IC interface, fortifies the vulnerable regions of the coating, and boosts its resistance to thermal shock. With the increase of YSZ thickness, stress on the surface of the DCL coating increases and the horizontal cracks extend to each other, resulting in laminar stripping and peeling cracking phenomenon on the surface of the coating and makes the position with greater stress fall into the LGYYSZ layer. Thus, the interface stress level and the interface cracking risk of TC/IC decreases. At a YSZ layer thickness of 200 mu m, the coating exhibits the maximum thermal shock resistance, achieving a lifespan of 178 cycles. In summary, a properly selected transition layer thickness can effectively redirect stress concentration and alter failure locations, thereby enhancing the thermal cycle life of the LGYYSZ/YSZ TBC.