Abstract This study investigated laser powder bed fusion (LPBF) additive manufacturing of H13 tool steel to identify how laser power (P) and scan speed (V) influenced melt pool geometry, microstructure, and susceptibility to cracking. Sequential studies from tracks, pads to 3D cubes were performed. Tracks and pads were made by laser scan on H13 build plates with and without powder addition. P-V windows were identified where keyholing, balling and under-melt occurred. The only change in melt pool geometry between the powder and no-power experiments was a slight shift of P-V window for the onset of balling. An inhomogeneous microstructure was observed for some tracks and pads, with a cellular-network microstructure and isolated-whisker microstructure at different regions in the same melt pool. Cracks were found in the regions with the isolated-whisker microstructure. Based on these observations, P-V windows of higher and lower cracking tendency were predicted. 3D-cubes built by P-V sets in different windows showed crack densities in line with the predictions. The results of this study provide guidance for LPBF process control to obtain uniform microstructure and minimize cracking of H13 steel parts.

中文翻译：

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使用单轨、多轨垫和3D立方体激光粉末床融合生产H13工具钢的微观结构和开裂行为研究

摘要 本研究调查了 H13 工具钢的激光粉末床融合 (LPBF) 增材制造，以确定激光功率 (P) 和扫描速度 (V) 如何影响熔池几何形状、微观结构和开裂敏感性。进行了从轨道、垫到 3D 立方体的顺序研究。轨道和垫是通过激光扫描在 H13 构建板上添加和不添加粉末制成的。PV 窗在出现锁孔、球化和熔化不足的地方被确定。粉末和无功率实验之间熔池几何形状的唯一变化是球化开始时 PV 窗口的轻微移动。对于一些轨道和焊盘，观察到不均匀的微观结构，在同一熔池的不同区域具有蜂窝状网络微观结构和孤立的晶须微观结构。在具有孤立晶须微观结构的区域中发现了裂纹。基于这些观察，预测了较高和较低开裂趋势的 PV 窗口。在不同窗口中由光伏组构建的 3D 立方体显示出与预测一致的裂缝密度。本研究的结果为 LPBF 过程控制提供了指导，以获得均匀的微观结构并最大限度地减少 H13 钢零件的开裂。