The influence of the laser scan strategy on grain structure and cracking behaviour in SLM powder-bed fabricated nickel superalloy
The influence of the laser scan strategy on grain structure and cracking behaviour in SLM powder-bed fabricated nickel superalloy
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DOI：
10.1016/j.jallcom.2014.06.172
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发表时间：
2014-12-05
影响因子：
6.2
通讯作者：
Attallah, Moataz M.
中科院分区：
文献类型：
--
作者：
Carter, Luke N.;Martin, Christopher;Attallah, Moataz M.
在镍高温合金CM247LC的选择性激光熔化（SLM）粉末床制造的工艺路线的开发过程中，已经观察到，作为Concept Laser M2 SLM粉末床制造标准的“岛”扫描策略，床系统强烈地影响材料的晶粒结构。光学和SEM显微照片显示在SLM制造和热等静压（热等静压处理）材料。晶粒结构中显示的重复图案与Concept Laser M2粉末床设施中用作标准的“岛”图案的重叠有关。有人建议，这种双模态晶粒结构的形成可以链接到从凝固熔池的热传递。一个“带”加热效应在每个“岛”，而不是“移动点”加热的概念已经提出，并已支持电子背散射衍射（EBSD）的证据。为了进行比较，还提供了使用简单的“来回”策略形成的样品的EBSD图，并揭示了显着不同的晶粒结构和晶体取向。示出了在所制造的材料中，由“岛”扫描引起的双峰结构，该策略直接转化为与可γ硬化材料的SLM制造相关的大范围焊接裂纹区域的宏观图案。类似的microCT数据表明，热等静压可以有效地封闭内部裂纹，以提供修复解决方案。(C)2014作者由爱思唯尔公司出版
During the development of a processing route for the Selective Laser Melting (SLM) powder-bed fabrication of the nickel superalloy CM247LC it has been observed that the 'island' scan-strategy used as standard by the Concept Laser M2 SLM powder-bed system strongly influences the grain structure of the material.Optical and SEM micrographs are presented to show the observed grain structure in the SLM fabricated and Hot Isostatically Pressed (HIPped) material. The repeating pattern shown in the grain structure has been linked to the overlapping of the 'island' pattern used as standard in the Concept Laser M2 powder-bed facility. It is suggested that the formation of this bi-modal grain structure can be linked to the heat transfer away from the solidifying melt pool. The concept of a 'band' heating effect across each 'island' rather than 'moving point' heating has been suggested and has been supported by Electron Back Scattered Diffraction (EBSD) evidence. For comparison an EBSD map from a sample formed using a simple 'back-and-forth' strategy has also been presented and reveals a dramatically different grain structure and crystallographic orientation.MicroCT evidence, supported by SEM microscopy, shows that in the as-fabricated material the bimodal structure caused by the 'island' scan-strategy translates directly into the macroscopic pattern for the regions of extensive weld cracking associated with the SLM fabrication of gamma' hardenable materials. Similar microCT data has shown that HIPping can effectively close the internal cracks to provide a retro-fix solution. (C) 2014 The Authors. Published by Elsevier B.V.