Self‐Healing and Corrosion Resistance of TiSi 2 ‐Modified Yb 2 Si 2 O 7<
Longhui Wang, Jinping Du, Weiran Zhang, Duan Li, Rongjun Liu, Yanfei WangABSTRACT
SiC f /SiC composites, promising for hot‑section components, are vulnerable to water vapor–oxygen corrosion at high temperatures. Thus, environmental barrier coatings (EBCs) are needed to provide corrosion protection. In this work, TiSi 2 was incorporated into Yb 2 Si 2 O 7 ‐based EBCs as a second phase at various addition levels, and the composite coatings were deposited on SiC f /SiC composites by atmospheric plasma spraying. Their phase evolution, microstructure, and corrosion behavior were systematically investigated during 160 h of water vapor–oxygen corrosion testing at 1300°C. The failure of fully encapsulated coatings follows a three‐stage progression: joint cracking, crack propagation, and side coating spallation, with interface junctions acting as preferential attack sites. A moderate addition of TiSi 2 (4 wt%) exhibited the best overall corrosion performance among the investigated compositions under the present experimental conditions, preserving intact surface morphology and structural continuity after 160 h, whereas an excessive addition induces severe oxidation, increased porosity, and spalling. The observed local crack‐closure behavior is consistent with the preferential oxidation of TiSi 2 to TiO 2 and SiO 2 , followed by reaction of TiO 2 with Yb 2 Si 2 O 7 to form Yb 2 Ti 2 O 7 , which were observed in association with local crack‐filling and bridging in a striped pattern, may therefore contribute to partial crack closure and retard further coating degradation. This study reveals the coupled crack‐healing‐related oxidation and coating‐failure processes. A rational strategy of addition balances healing efficiency and structural stability, offering a viable route toward durable EBCs with extended service lives under extreme conditions.