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 x 10(-3) mu m(2) s(-1) at 1300 degrees C, 7.99 x 10(-3) mu m(2) s(-1) at 1330 degrees C, and 1.86 x 10(-2) mu m(2) s(-1) at 1340 degrees 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 degrees C does not conform the Arrhenius equation because of the undissolved gamma ' phase.