Thermal shock resistance and failure analysis of La2(Zr0.75Ce0.25)2O7-based TBCs produced by atmospheric plasma spraying

Abstract

High-temperature thermal barrier coatings (TBCs) have important application prospects in the high-performance gas turbine. It is of great significance to study the thermal shock behaviors in improving the reliability and durability of TBCs. In this study, three groups of high-temperature La2(Zr0.75Ce0.25)2O7 (LCZ)-based coatings (LCZ, LCZ/8YSZ and LCZ/CYSZ) were designed and produced by atmospheric plasma spraying. Two cooling ways, water cooling and air cooling, were employed to conduct the thermal shock tests, which facilitates a comprehensive understanding of the thermal shock resistance and the failure mechanisms of LCZ-based TBCs in cyclic thermal shocks. The thermal shock resistance of these coatings was evaluated by thermal cycling lifetime and the failure mechanisms were analyzed in the framework of crack initiation and propagation. Based on the present results, LCZ/8YSZ coating remains intact after 100 air-cooled thermal shock cycles, indicative of remarkable thermal shock resistance. The initiation and propagation of transverse cracks at the interface between the ceramic layer and bond coat result in interface debonding, which is the only failure mechanism of these coatings in air-cooled thermal shock. Except for the interface debonding, in water-cooled thermal shock, the spalling of top coat is another failure mechanism due to the intersection of vertical cracks and interlayer microcracks. The main reasons for the growth of these cracks were also discussed and analyzed in detail.