Effect of substrate orientation on the columnar-to-equiaxed transition in laser surface remelted single crystal superalloys
Effect of substrate orientation on the columnar-to-equiaxed transition in laser surface remelted single crystal superalloys
复制标题
基体取向对激光表面重熔单晶高温合金柱状到等轴转变的影响
DOI：
10.1016/j.actamat.2015.01.063
复制
发表时间：
2015-04-15
期刊：
影响因子：
9.4
通讯作者：
Zheng, Y. P.
中科院分区：
文献类型：
--
作者：
Wang, L.;Wang, N.;Zheng, Y. P.
For a successful repair of single-crystal (SX) components, an epitaxial growth of columnar dendrites is required, i.e. a columnar to equiaxed transition (CET) has to be avoided. In this study it was found that changing the angles of laser treatment with respect to the standard orientation [100](001) can have a strong and positive effect on the quality of the part. By rotating the SX substrate around x-, y-, and z-axis, which coincide with the [100], [010], and [001] crystallographic directions, respectively, the effect of the substrate orientation for different rotation angles on the columnar-to-equiaxed transition (CET) in laser remelting process was determined. It was found that from the [100] (001) initial state, the CET varies strongly with the substrate orientation when the rotation is made around the y-axis, whereas there is nearly no change when the rotation is performed around the x- or z-axis. This drastic difference is caused by the fact that for rotation around the y-axis by 45 the melt pool contains no intersection point where dendrite domains with three preferred (100) growth directions meet. For the rotation about the x or z-axis, at least one intersection point appears. The intersection point is the most vulnerable place for the CET since the thermal gradient tends to reach its minimal value there. The number and location of the intersection points jointly control the overall CET tendency. Reducing those points and/or moving them to the positions with high thermal gradient are beneficial for avoiding CET generally. Our results clearly demonstrate that the laser processing window for the repair of the single crystal superalloy can be enlarged if the substrate orientation is rotated correspondingly. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
