SiC modified self-healing ytterbium disilicate materials for potential environmental barrier coating application

Environmental barrier coatings (EBCs) are crucial to the reliability and durability of SiCf/SiC composite components seeking applications in hot sections of next-generation advanced aero-engines. The cracks initiated and developed in EBCs owing to various reasons during service greatly undermine their lifespans. To address this problem, in this work, silicon carbide (SiC) in the forms of particles and whiskers with various amounts have been introduced to ytterbium disilicate (Yb2Si2O7), the mainstream EBC topcoat materials, so as to gain some self-healing potential. The results reveal that, the SiC inclusions in Yb2Si2O7 in the presence of ytterbium monosilicate (Yb2SiO5) can trigger the following reactions. Specifically, SiC self-healing agents are oxidized to form viscous SiO2, which actively reacts with Yb2SiO5 upon encountering it, forming Yb2Si2O7. This has brought twofold beneficial effects including ① silicon supplementation of disilicate topcoat, whose silicon element tends to be dragged out by water vapor, leading to the deterioration of thermal mismatch; as well as ② crack self-healing resulting from the volume expansion induced by the above reactions. Then the two aspects of self-healing agents, namely the promptness and sustainability, have been discussed in detail. The former is unveiled to be more pertinent to the repairing of large cracks, whilst the latter is more relevant to the self-healing of tiny cracks at initiation or early stage of propagation. The current work sheds some lights on the design and development of more durable and robust EBCs with self-healing capability.

Automated summary

In this study, SiC particles and whiskers with various amounts were introduced to Yb2Si2O7, the mainstream EBC topcoat materials, to enhance their self-healing capability. The SiC inclusions in the presence of Yb2SiO5 triggered reactions that resulted in the formation of Yb2Si2O7, which increased silicon supplementation and enabled crack self-healing. This research provides insights for the design and development of more durable and robust EBCs with self-healing capability.