Solidification characteristics and as-cast microstructure of Rhenium-Containing single crystal superalloys under high thermal gradient directional solidification

A series of Ni-base single crystal superalloys with increasing contents of Re (3-6 wt. %) were directionally solidified under a high thermal gradient of approximately 250 K/cm. It shows that Re additions slightly increases the liquidus temperature, but decreases the eutectic reaction and solvus temperature of the experimental alloys. EPMA analysis indicates that Re addition strongly influences the segregation ratios of the constituent elements, particularly for Cr, Mo and W, and thus results in more severe dendrite segregation and large amount of eutectic formation in the as-cast microstructures.