On the Fabrication of Defect-Free Nickel-Rich Nickel–Titanium Parts Using Laser Powder Bed Fusion
On the Fabrication of Defect-Free Nickel-Rich Nickel–Titanium Parts Using Laser Powder Bed Fusion
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利用激光粉末床熔融制造无缺陷富镍镍钛零件
DOI：
10.1115/1.4054935
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Elwany, Alaa
中科院分区：
文献类型：
--
作者：
Zhang, Chen;Xue, Lei;Atli, Kadri C.;Arróyave, Raymundo;Karaman, Ibrahim;Elwany, Alaa
激光粉末床熔合（L-PBF）增材制造（AM）是制造具有复杂几何形状、独特功能性能和定制材料成分的镍钛（NiTi）形状记忆合金（sma）的有效方法。然而，随着NiTi粉末原料中Ni含量的增加，由于出现翘曲、边角升高、分层、表面粗糙度过大等宏观缺陷，生产高质量零件的能力明显降低。本研究探讨了富镍NiTi粉末的可印刷性，其中可印刷性是指制造无宏观缺陷部件的能力。具体而言，首先进行了单轨迹实验，以选择立方体试样制备的关键工艺参数设置。采用机器学习分类技术预测可打印空间。通过进一步的立方试样制备验证了预测的可打印空间的可靠性，并研究了工艺参数与潜在宏观缺陷模式之间的关系。结果表明，激光功率对高Ni含量NiTi粉末的可打印性至关重要。在低激光功率设置下（P < 100 W），可打印空间相对较宽，分层是主要的宏观缺陷模式。在亚高激光功率条件下（100 W≤P≤200 W），不同的扫描速度和不同的缝隙间距组合下，可打印空间被缩小到一个低缝隙间距区域，存在翘曲、边缘/角落升高等宏观缺陷，并出现分层现象。当激光功率进一步增大（P < 0 > 200 W）时，表面出现粗糙缺陷，导致可打印空间进一步缩小。
Laser powder bed fusion (L-PBF) additive manufacturing (AM) is an effective method of fabricating nickel–titanium (NiTi) shape memory alloys (SMAs) with complex geometries, unique functional properties, and tailored material compositions. However, with the increase of Ni content in NiTi powder feedstock, the ability to produce high-quality parts is notably reduced due to the emergence of macroscopic defects such as warpage, elevated edge/corner, delamination, and excessive surface roughness. This study explores the printability of a nickel-rich NiTi powder, where printability refers to the ability to fabricate macro-defect-free parts. Specifically, single track experiments were first conducted to select key processing parameter settings for cubic specimen fabrication. Machine learning classification techniques were implemented to predict the printable space. The reliability of the predicted printable space was verified by further cubic specimens fabrication, and the relationship between processing parameters and potential macro-defect modes was investigated. Results indicated that laser power was critical to the printability of high Ni content NiTi powder. In the low laser power setting (P < 100 W), the printable space was relatively wider with delamination as the main macro-defect mode. In the sub-high laser power condition (100 W ≤ P ≤ 200 W), the printable space was narrowed to a low hatch spacing region with macro-defects of warpage, elevated edge/corner, and delamination happened at different scanning speeds and hatch spacing combinations. The rough surface defect emerged when further increasing the laser power (P > 200 W), leading to a further narrowed printable space.