Influence of doping element segregations on the solution and diffusion properties of hydrogen in γ/γ′ interface of DZ411 superalloy

Abstract

First-principles calculations are employed to examine H solution and diffusion at the Co and Ta-doped γ/γ′ interface of DZ411 superalloy. Co and Ta prefer to occupy M1 sites within the γ phase, and octahedral (O) traps are more stable for H adsorption than tetrahedral (T) traps. O1 trap at interface showing the lowest solution energy of 0.23 eV, suggesting a preference H adsorption trap at the doped interface. Two diffusion pathways are considered: parallel and perpendicular to the interface. In the parallel direction, H diffusion is easier in the γ′ phase, with the lowest diffusion barrier of 0.33 eV in layer 2. Vertical diffusion of H along both tetrahedral and octahedral paths is hindered by Co and Ta doping, with Ta having a slightly stronger effect, increasing the diffusion barrier by 0.05 eV compared to Co. Diffusion coefficients show H diffusivity at the doped interface is 2 orders of magnitude lower than at the perfect interface, with values of 10-10 cm2/s for the doped interface compared to 10-8 cm2/s for the perfect interface. Partial density of states analysis reveals that H adsorption and diffusion are influenced by hybridization with the trap atom orbitals. These results provide insights into hydrogen resistance in DZ411 superalloy.