In situ synchrotron X-ray imaging of 4140 steel laser powder bed fusion
In situ synchrotron X-ray imaging of 4140 steel laser powder bed fusion
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DOI：
10.1016/j.mtla.2019.100306
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发表时间：
2019-06-01
期刊：
影响因子：
3.4
通讯作者：
Sun, Tao
中科院分区：
文献类型：
--
作者：
Bobel, Andrew;Hector, Louis G., Jr.;Sun, Tao
采用同步辐射X射线成像技术，在移动激光源上对AISI 4140铁素体-贝氏体钢的激光粉末床熔合（LPBF）进行了研究。由于4140在增材制造文献中只受到很少的关注，因此重点关注熔池动力学、蒸汽腔深度、构建层高度和孔隙率起源对4140构建后微观结构的影响。应用了四个构建参数集，这些参数集能够改变激光功率、扫描速度、激光光斑尺寸和比能量密度（SED）。蒸汽腔和熔池深度测量每个单轨道激光扫描。LPBF过程的直接成像表明，无论构建参数设置如何，构建中孔隙率的主要来源都来自粉末中夹带的气体。高分辨率SEM和EBSD表明，在广泛的SED范围内，随着构建参数的设置，构建后的微观结构没有显著变化。观察到的快速凝固速率（0.06-0.08 m/s）导致精细的马氏体包/块尺寸分布（1-3 μ m），具有增加材料强度的潜力。
An in situ synchrotron X-ray imaging technique was used to examine laser powder bed fusion (LPBF) of a chrome-molybedum, AISI 4140, ferrite-bainite steel, from a moving laser source. Since 4140 has received only minimal attention in the AM literature, focus here was on the effects of melt pool dynamics, vapor cavity depths, build layer height, and the origin of porosity on the 4140 as-built microstructure. Four build parameter sets, which enabled variation of laser power, scan speed, laser spot size, and specific energy density (SED), were applied. Vapor cavity and melt pool depths were measured for each single-track laser scan. Direct imaging of the LPBF process demonstrated that the primary source of porosity in the build originates from incorporation of entrapped gas within the powder irrespective of build parameter set. High resolution SEM and EBSD demonstrated that the as-built microstructure did not vary significantly with build parameter set over a broad range of SED. The fast solidification rates observed (0.06-0.08 m/s) lead to fine martensite packet/block size distributions (1-3 mu m) with the potential for increased material strength.