型壳中央散热对一种单晶高温合金凝固组织与持久性能的影响

Effects of Ceramic Shell Mold with Central Heat Radiation on Solidification Microstructures and Stress Ruptre Property of a

摘要:

单晶凝固过程中温度场均匀性控制对单晶制备过程特别重要。本文以国内广泛应用的第二代单晶高温合金DD6为研究对象，研究型壳中央散热对其凝固组织与持久性能的影响。结果表明，与合金中柱型壳相比，石墨中柱型壳能有效地改善单晶凝固过程中温度场的均匀性，提高温度梯度，有利于保持单晶凝固过程中热流方向的平直。因此，石墨中柱型壳有利于降低一次枝晶间距，细化γ-γ’共晶相，减少单晶生长方向与[001]方向的角度差，使单晶高温合金获得较高的持久寿命。

Abstract:

The control of the temperature field during single crystal solidification has an important effect on single crystal growth. The present paper studied the influence of ceramic shell mold with central heat radiation on the microstructures and stress rupture property of the widely used DD6 single crystal superalloy. The results indicated that the mold with graphite center pillar could improve the uniformity of the temperature field and the temperature gradient during the solidification, and it could make the direction of heat flow more straight. As a result, the primary dendrite arm spacing decreased, the size and the volume fraction of γ-γ'' eutectic were reduced, the angle between the single crystal growth orientation and the [001] orientation decreased, so the single crystal superalloy can achieve longer stress rupture life.