DFT-assisting experimental insights into interfacial inter-diffusion of TBCs with Cr₂AlC as the bond coat

Cr₂AlC exhibits unique high-temperature properties, positioning it as a promising bond coat in thermal barrier coatings (TBCs), but its practical application is limited by severe interfacial inter-diffusion with Ni-based superalloys. Herein, with the directionally solidified Ni-based superalloy IC10 as the substrate, the interfacial inter-diffusion of TBCs with Cr₂AlC as the bond coat was investigated at 900–1100°C for 1–10 h experimentally in combination of density functional theory (DFT) simulations. The distinct diffusion regions, primarily composed of NiAl, appeared at the Cr₂AlC/IC10 interface, around which Al and Ni atoms showed higher diffusivity than Cr atoms. Of much interest, their estimated diffusion activation energies (E_d) at 1.51±0.06 eV, 2.51±0.39 eV and 3.36±0.63 eV were consistent with the calculated ones at 1.57–2.34 eV, 1.92–2.82 eV and 2.42–3.89 eV by DFT simulations based on the experimental interfacial structures via TEM, confirming the dominant role of Al and Ni atoms in the interfacial inter-diffusion. Furthermore, the calculated electronic structure and bond stiffness showed a critical role of relevant bond strength in their E_d, suggesting a promising means to tune the interfacial inter-diffusion between Cr₂AlC and superalloys by modifying the bond strength, such as elemental doping.