The effect of welding conditions on stray grain formation in single crystal welds – theoretical analysis
The effect of welding conditions on stray grain formation in single crystal welds – theoretical analysis
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DOI：
10.1016/j.actamat.2004.08.039
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发表时间：
2005-01
期刊：
影响因子：
9.4
通讯作者：
J. Vitek
中科院分区：
文献类型：
--
作者：
J. Vitek
镍基单晶高温合金焊缝在凝固过程中产生杂晶，导致力学性能下降和开裂。基于成分过冷提前推进枝晶生长前沿的机制，焊接条件（焊接速度和功率）的影响，在凝固过程中形成杂散晶粒的倾向进行了评估。一个简单的三维热模型结合几何模型，以确定杂散晶粒形成的程度作为焊接条件和位置的函数在焊接池中，考虑到枝晶生长方向的影响。计算了描述杂散晶粒形成程度的参数，该参数在整个凝固前沿上平均。开发了显示杂散晶粒形成的严重程度作为焊接速度、功率和方向的函数的加工图。结果发现，低功率和高焊接速度是最佳的杂散晶粒形成的潜力最小化。焊缝的晶体取向对形成杂散晶粒的总体趋势的影响是最小的，尽管基于取向的局部变化被量化。将理论分析与激光焊接镍基单晶的早期实验工作进行了比较，所有实验观察结果都可以在计算中重现。
Stray grain formation during solidification of nickel-based single crystal superalloy welds leads to a degradation of mechanical properties and cracking. Based on the mechanism of constitutional supercooling ahead of the advancing dendritic growth front, the effect of welding conditions (weld speed and power) on the tendency to form stray grains during solidification was evaluated. A simple 3D thermal model was combined with a geometric model to determine the extent of stray grain formation as a function of welding conditions and position in the weld pool, taking into account the influence of dendrite growth orientation. A parameter describing the degree of stray grain formation, averaged over the entire solidification front, was calculated. Processing maps that show the severity of stray grain formation as a function of weld speed, power and orientation were developed. It was found that low power and high weld speed were optimal for minimizing the stray grain formation potential. The effect of crystallographic orientation of the weld on the overall tendency to form stray grains was minimal, although local variations based on orientation were quantified. The theoretical analysis was compared to earlier experimental work on laser welded nickel-based single crystals and all of the experimental observations could be reproduced in the calculations.