| 摘要 |
Directional solidification of a single crystal superalloy article may be accomplished using a mold (20) with a starter section (36, 38), and a selector section (28) to convert columnar growth from the starter into single crystal growth. In such a process, the deviation of [001] crystallographic orientation with respect to the longitudinal axis of the article being formed is reduced from 9 degrees to 5 degrees by controlling the heat transfer in the starter section. A stepped starter section, wherein the lower subsection (38) has a volume of 52-98% of the total starter volume, and wherein the upper subsection (36) is relatively small in lateral dimension, has been found most useful. When the solidification interface moves into the smaller width upper subsection, it becomes more nearly planar, and results in improved columnar growth in the starter, and in reduction in the crystallographic deviation of the article. |
