Changes in the Diffusion Coefficient of Rhenium in a New Type of Nickel‐Based Single‐Crystal Superalloy during Homogenization

Rhenium (Re) is the slowest‐diffusing element in nickel‐based single‐crystal (SC) superalloy, and its diffusion coefficient has deep influence on the research of homogenization. A model of diffusion of Re during homogenization is established in this work. Based on the model and the data in this experiment, the diffusion coefficient of Re (D_Re) is 6.67 × 10⁻³ μm² s⁻¹ at 1300 °C, 7.99 × 10⁻³ μm² s⁻¹ at 1330 °C, and 1.86 × 10⁻² μm² s⁻¹ at 1340 °C. The experimental data show that the D_Re in SC structure is smaller than it in polycrystalline structure, which was measured by diffusion couple system. Also, the law of change of D_Re during 1300–1340 °C does not conform the Arrhenius equation because of the undissolved γ′ phase.