Effect of Ru on interdiffusion dynamics of β-NiAl/DD6 system: A combined experimental and first-principles studies

As a diffusion barrier between thermal barrier coating (TBC) and advanced single crystal (SC) superalloy DD6, RuNiAl coating has attracted increasing attention recently. In this work, different diffusion couples including NiAl/DD6, RuNiAl/DD6 and RuAl/DD6, were prepared and their interdiffusion behavior was investigated at 1100 degrees C, to understand the diffusion barrier mechanism of the RuNiAl coating. The addition of Ru to NiAl effectively reduced the interdiffusion coefficient of Al, thereby delaying the phase transformation from beta to gamma' and suppressing the formation of topologically closed-packed (TCP) phases and primary interdiffusion zone (IDZ). It is verified by first-principles calculations that Ru restrained the formation of Ni and Al vacancies and Ni and Al antisite atoms. According to the calculations, the addition of Ru increases the defect formation energies, thus inhibiting the diffusion of Al in beta-NiAl. The calculation results are consistent with the experimental data. (C) 2015 Elsevier Ltd. All rights reserved.