Effects of Ru on Solidification Characteristic and Microstructures of Ni-Based Single Crystal Superalloy

The Ru-free and Ru-containing single crystal superalloys were cast in the directionally solidified furnace, while other alloying element contents were basically kept unchanged. The effects of Ru on the solidification characteristic and microstructures of single crystal superalloy were investigated with differential scanning calorimetry, electron probe micro analyzer, energy-dispersive X-ray spectroscope, scanning electron microscope and transmission electron microscope. The results show that the liquidus temperature of the single crystal superalloy decreases with Ru addition. The primary dendrite arm spacing and volume fraction of γ/γ′ eutectic both decrease with Ru addition. The sizes of γ′ phase of dendritic core and interdendritic region have no obvious change with Ru addition. Ru tends to segregate slightly in the dendritic core. The extent of elements segregation decreases with the Ru addition. Ru tends to partition preferentially into the γ matrix. The addition of Ru decreases the partition ratio (the ratio of the γ phases composition over the γ′ phases composition) of elements Re, W and Mo.