Hierarchical crack-path regulation in Yb2SiO5/(Yb2SiO5–Yb2Si2O7)/Si environmental barrier coatings: mechanisms and design principles

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The Yb 2 SiO 5 /(Yb 2 SiO 5 –Yb 2 Si 2 O 7 )/Si trilayer environmental barrier coating (EBC) has garnered significant attention in recent years for its excellent corrosion resistance and thermal compatibility with SiC f /SiC. Under thermal cycling, surface vertical cracks initiate and propagate downward, branch and coalesce within the interlayer, ultimately leading to coating delamination and failure. This study employs the finite element method to quantitatively elucidate the influence of interlayer composition and surface crack density on integrated crack propagation behavior. Three critical crack propagation mechanisms are systematically analyzed, including effect of inter-crack elastic shielding within Yb 2 SiO 5 top coat on suppressing the downward propagation, the competition between deflection and penetration at the Yb 2 SiO 5 /(Yb 2 SiO 5 –Yb 2 Si 2 O 7 ) interface, and composition-driving crack bifurcation geometry within the (Yb 2 SiO 5 –Yb 2 Si 2 O 7 ) interlayer. Based on these insights, an optimal surface crack geometry and interlayer compositions are proposed enables stable crack arrest, controlled interfacial deflection, and moderate-energy-dissipative branching, thereby maximizing structural toughness and extending service lifetime.