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Abstract

High-temperature mechanical properties of Ni-based superalloys can be significantly improved by adding refractory alloying elements, such as Re, Mo or W. However, due to the complexity of the interplay between composition and microstructure the effect of these additives is only understood in a phenomenological way. Within this work, we investigate the diffusion and segregation behavior of alloying elements in Ni-based superalloys using a combination of ab-initio DFT calculations and kinetic Monte Carlo (kMC) modeling, with a particular focus on Re and its interplay with the γ/γ' phase interface. Re is known to be one of the slowest-diffusing elements in Ni [1], and is one of the most effective, and expensive, alloying additives currently in use. In this combined approach, DFT provides insights into local electronic properties of the γ/γ' interface and Re substitutional defects as well as into energetics of microscopic diffusion processes. Based on DFT data, a kMC model is developed to analyze diffusion and segregation behavior of alloying elements on an extended time scale. [1] M. S. A. Karunaratne, P. Carter, R. C. Reed, Mat. Sci. Eng. A 281, 229 (2000)