• • 0.5 wt.% Y2O3 doping at 1100 °C suppresses the parabolic rate constant by shifting scale growth from mixed diffusion to inward oxygen diffusion control, directly extending service life of Cr2AlC components in turbine and furnace environments where Al depletion typically limits lifetime to <1000 h.
• • Undoped Cr2AlC undergoes a 39.9% volume contraction due to sub-surface Cr7C3 formation, generating tensile stresses that cause scale spallation; 0.5 wt.% Y2O3 completely suppresses this phase transformation, eliminating a primary failure mode in high-temperature structural ceramics.
• • Y3+ segregation at α-Al2O3 grain boundaries via the 'site blocking' effect inhibits outward Al3+ short-circuit diffusion, reducing Al reservoir depletion rates and preventing Kirkendall void nucleation at the α-Al2O3/Cr7C3 interface—a critical degradation mechanism in undoped specimens.
• • DFT calculations confirm intrinsically higher interfacial bonding strength for α-Al2O3/Cr2AlC compared to α-Al2O3/Cr7C3, combined with mechanical interlocking from Y-rich oxide pegs, yielding a void-free interface that sustains adhesion under thermal cycling without spallation.