Investigation on solidification path of Ni-based single crystal superalloys with different Ru contents

The solidification path of Ni-based single crystal superalloy with different Ru contents (0–4 wt%) was systematically investigated under planar and dendrite solid-liquid interface solidification conditions, aiming to reveal the evolution rule of solidification microstructure and selection mechanism of phases of the fourth generation single crystal superalloys. The results indicated that under plane solidification interface, the fine γ/γ′ eutectic structure started to form after the solidification of γ phase and then further developed the coarse γ/γ′ structure. The solidification finally terminated with the formation of β-NiAl phase enveloped by coarse γ′ phase for Ru-free superalloy. However, when Ru was added in superalloy, the β-NiAl phase was firstly precipitated after the solidification of γ phase, and no fine γ/γ′ structure connecting the γ phase with β-NiAl phase was found. Under the dendrite solid-liquid interface condition, the solidification path was consistent with that in the plane one. The evolution mechanism of solidification path with different Ru contents was discussed, which was helpful to optimize the alloy composition design.