Thermal cycling and steam corrosion behavior of Yb ₃ Al ₅ O ₁₂ ‐based multilayered environmental barrier coatings for SiC _f /SiC

Abstract To alleviate thermal mismatch problem of environmental barrier coatings (EBCs) on SiC fiber‐reinforced SiC ceramic matrix composites (SiC f /SiC CMCs) surface and improve their high‐temperature durability for aircraft engines, by fully utilizing the appropriate thermal expansion coefficient, low oxygen transmittance, low thermal conductivity, and other advantages of ytterbium aluminum garnet (Yb 3 Al 5 O 12 ), the double ceramic layered Yb 3 Al 5 O 12 /Yb 2 Si 2 O 7 (DCL‐Yb 3 Al 5 O 12 ) and the triple ceramic layered Yb 3 Al 5 O 12 /Yb 2 SiO 5 /Yb 2 Si 2 O 7 (TCL‐Yb 3 Al 5 O 12 ) EBC systems were prepared on SiC f /SiC CMCs by atmospheric plasma spraying (APS). Their phase composition and microstructures were investigated comparatively. The thermal cycling and water vapor/oxygen corrosion behavior of these coating systems were compared at 1300°C. The results showed that the thermal cycling life of the DCL‐Yb 3 Al 5 O 12 and TCL‐Yb 3 Al 5 O 12 EBC systems were 295 and 320 times, respectively. The failure of both the coating systems occurred between the Yb 2 Si 2 O 7 layer and Si bond coat. The strength retention rate of DCL‐Yb 3 Al 5 O 12 and TCL‐Yb 3 Al 5 O 12 EBC systems after water vapor/oxygen corrosion for 70 h was 12.8% and 23.1%, respectively, and the fracture modes of both the systems exhibited “pseudoplastic” characteristic. TCL‐Yb 3 Al 5 O 12 EBC systems with a gradient structure of more layers exhibit more excellent high‐temperature durability than DCL‐Yb 3 Al 5 O 12 EBCs.