Single crystal Ni-based superalloys are the typical structural materials for high-pressure turbine blades, and their microstructure is critical in determining their mechanical properties. The withdrawal rate is a key parameter affecting the microstructure during the single crystal growth process. In the present work the effect of the withdrawal rate on the microstructure of a third-generation single crystal superalloy containing 6.8 ​wt% Re has been investigated, and the creep resistance of the alloy determined. The results showed that increased withdrawal rate refined the dendritic structure, reduced dendritic arm spacing, promoted the growth of secondary tertiary dendrites and decreased solidification segregation with a reduced size of γ′ phase. The porosity density of the as-cast alloy first decreased and then increased with the withdrawal rate, while the minimum porosity densityoccurred when the alloy was under the solidification condition of withdrawal rate of 4.5 ​mm/min. The maximum creep rupture life of 326.4 ​h of the heat-treated alloys under the test condition of 1100 ​°C/140 ​MPa also appeared at the alloys under the withdrawal rates of 4.5 ​mm/min. It is believed that the minimum porosity density and reduced size of the γ′ phase may be the main reasons for the enhanced creep rupture life of the alloys with withdrawal rates of 4.5 ​mm/min. This investigation provides theoretical support and a practical basis for the development of third-generation single crystal superalloys.

单晶镍基高温合金是高压涡轮叶片的典型结构材料，其微观结构对其力学性能至关重要。拔出速率是影响单晶生长过程中微观结构的关键参数。在目前的工作中，研究了拉拔速率对含有 6.8 wt% Re 的第三代单晶高温合金微观结构的影响，并确定了合金的抗蠕变性。结果表明，提高拔出率细化了枝晶组织，减小了枝晶臂间距，促进了二次三次枝晶的生长，减少了凝固偏析，γ′相尺寸减小。铸态合金的孔隙密度随着拔模速度的增加先减小后增大，而最小孔隙密度出现在合金处于拔出速率为4.5 mm/min的凝固条件下。热处理合金在1100℃/140MPa试验条件下的最大蠕变断裂寿命为326.4h，也出现在4.5mm/min拉拔速率下的合金。认为最小孔隙密度和γ'相尺寸减小可能是拔模速率为4.5mm/min时合金蠕变断裂寿命提高的主要原因。该研究为第三代单晶高温合金的开发提供了理论支持和实践依据。1100℃/140MPa试验条件下热处理合金4h，在4.5mm/min拉拔速率下的合金也出现了脱模现象。认为最小孔隙密度和γ'相尺寸减小可能是拔模速率为4.5mm/min时合金蠕变断裂寿命提高的主要原因。该研究为第三代单晶高温合金的开发提供了理论支持和实践依据。1100℃/140MPa试验条件下热处理合金4h，在4.5mm/min拉拔速率下的合金也出现了脱模现象。认为最小孔隙密度和γ'相尺寸减小可能是拔模速率为4.5mm/min时合金蠕变断裂寿命提高的主要原因。该研究为第三代单晶高温合金的开发提供了理论支持和实践依据。