Effect of Ruthenium on Precipitation Behavior of the Topologically Close-Packed Phase in a Single-Crystal Ni-Based Superalloy During High-Temperature Exposure

The precipitation behaviors of the topologically close-packed (TCP) phase in the Ru-free and Ru-containing single-crystal Ni-based superalloys have been investigated. All the TCP phases have been identified as the μ phase with large numbers of planar defects by using a scanning transmission electron microscope (STEM). The addition of 3 wt pct Ru effectively suppresses the nucleation of the μ phase because the addition of 3 wt pct Ru not only decreases the supersaturation of γ phase but also increases the elastic strain energy for the nucleation of the μ phase. Additionally, the addition of 3 wt pct Ru makes more Re enter the μ phase during its growth and the critical nucleus radius of the μ phase becomes larger. Therefore, it is found that the addition of 3 wt pct Ru decreases the growth rate of the μ phase.