Effects of Re and Ru on the solidification characteristics of nickel-base single-crystal superalloys

The solidification characteristics, such as the phase transformation temperature and partition coefficient, were investigated in four Ni-base single-crystal superalloys with varied contents of Re and Ru. Differential scanning calorimetry (DSC) analysis reveals that the liquidus and solidus temperatures decrease with increasing levels of Re additions. However, the Ru only has negligible influences on the liquidus and solidus temperatures. The partition coefficient of constituent elements is investigated by using the directional solidification followed quenching (DSQ) technique. Re is found to reduce the segregation of Re and W, whereas Ru only has negligible effects on the segregation of Re and W. For comparison, the matrix scanning is performed on the representative dendritic structures. With increasing withdrawal rate, Re and Ru additions show the stronger influences on segregation behavior of alloying elements, particularly for Al and Ta.