Mechanism of hot crack propagation and prevention of crack formation during electron beam powder bed fusion of a difficult-to-weld Co-Cr-Ni-W superalloy
Mechanism of hot crack propagation and prevention of crack formation during electron beam powder bed fusion of a difficult-to-weld Co-Cr-Ni-W superalloy
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难焊Co-Cr-Ni-W高温合金电子束粉末床熔合热裂纹扩展机理及裂纹预防
DOI：
10.1016/j.jmatprotec.2021.117088
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发表时间：
2021
影响因子：
6.3
通讯作者：
Z.W. Chen
中科院分区：
文献类型：
--
作者：
M. Phan;D. Fraser;S. Gulizia;Z.W. Chen
了解电子束粉末床熔合 (EPBBF) 过程中难焊合金中的热裂纹如何传播对于制造优质零件至关重要。目前文献中的理解没有深入探讨裂纹扩展机制的足够细节。这项研究的主要部分旨在揭示 EBPBF 期间裂纹如何生长。使用难以焊接类型的钴基合金的 EBPBF 制作样品，并通过顺序切片抛光显示裂纹图案/网络，这是一种显示热裂纹网络的新方法。人们发现，当观察到表面裂纹时，它们往往垂直于扫描方向取向。每层扫描方向改变90°，表面裂纹也相应改变方向。观察了表面裂纹方向与顶层下方裂纹网络之间的关系。显示了裂纹网络如何生长以及液化如何帮助这种生长的识别。有时，即使顶层下方的裂纹网络不断发展，也发现表面裂纹不存在。没有表面裂纹的原因是在低切线角熔轨条件下形成的水平枝晶表面层的自然生长。因此，研究的第二部分是尝试利用水平枝晶来预防热裂纹。结果表明，受控重熔是保留每个扫描层中水平枝晶晶粒的有效方法，因此不会发生热裂纹。还将进一步表明，受控重熔有时会导致等轴晶粒长大。
Understanding how hot cracks propagate in difficult-to-weld alloys during electron beam powder bed fusion (EBPBF) is necessary for manufacturing quality parts. The current understanding in the literature does not go into sufficient details of the mechanisms of crack propagation. The major part of this study aimed to reveal how cracks grow during EBPBF. Samples were made using EBPBF of a Co-base alloy that is a difficult-to-weld type and crack patterns/networks were revealed through sequential sectioning-polishing, which is a new way of illustrating hot crack networks. It was found that when surface cracks were observed, they tended to orientate normal to the scan direction. The scan direction changed 90° after each layer and the surface cracks also changed orientations accordingly. The relationships between the crack orientations on the surface and the crack networks beneath the top layer were observed. The identification of how the crack networks had grown and how liquation had assisted this growth is shown. Sometimes surface cracking was found to be absent even though the crack network beneath the top layer kept developing. The lack of surface cracking is explained by the natural growth of a horizontal dendritic surface layer that is formed under the condition of a low tangent angle melt track. Thus, the second part of the study was an attempt to utilize horizontal dendrites for hot crack prevention. It will be shown that controlled remelting can be an effective method to preserve the horizontal dendrite grains in each scan layer and thus hot cracking does not occur. It will be further shown also that controlled remelting can occasionally result in equiaxed grain growth.
电子束粉末床熔合中控制局部热量积累以控制 Co-Cr-Mo 合金的质量和微观结构
影响因子：
3
作者：
Zhao Yufan;Koizumi Yuichiro;Aoyagi Kenta;Yamanaka Kenta;Chiba Akihiko
通讯作者：
Chiba Akihiko