Design and evaluation of multilayer Yb 4Hf 3O 12-based T/EBCs with enhanced thermal stability for high-temperature applications

Thermal/environmental barrier coatings (T/EBCs) systems are regarded as potential solutions to address the degradation challenges of ceramic matrix composites (CMCs) under extreme temperatures in aeroengine applications. Rare-earth hafnates are recognized as promising candidates for the top-layer materials of T/EBCs. In this work, Yb4Hf3O12/Yb2Si2O7/Si and Yb4Hf3O12/Yb2SiO5/Yb2Si2O7/Si T/EBCs systems were designed and fabricated via plasma spraying, and their isothermal oxidation and water-quenching thermal shock behaviors at 1500 °C were systematically evaluated. The results revealed that the T/EBCs system incorporating a Yb4Hf3O12 top layer exhibited excellent high-temperature performance and maintained its structural integrity at 1500 °C. Compared with the tri-layer system, the four-layer system demonstrated better oxidation and thermal shock resistance, which was attributed primarily to the incorporation of the Yb2SiO5 interlayer, which effectively enhanced the interfacial stability and mitigated the thermal expansion coefficient mismatch between adjacent layers, and reduced the stress fluctuations at the coating edges and interfaces. In a tri-layer system, the spallation of the top layer can be identified as an important failure mechanism. However, for both multilayer systems, the reduction in the Si bond layer emerged as a critical factor contributing to their high-temperature degradation.