In this study, the interfacial characteristics of materials deposited by hybrid metal additive manufacturing (AM) processes (laser powder bed fusion (L-PBFed) and directed energy deposition (DEDed)) were investigated. The deposition characteristics, microstructure, bonding properties, and crack propagation characteristics at the interface were analyzed with different relative building directions of L-PBFed and DEDed. The additional layers by DED were deposited on the top surface (L-PBFed-Tracked surface) and on the side (L-PBFed-Layered surface) of the substrate built by L-PBFed. Defects occurred at the interface between PBFed and DEDed during the DED process due to the oxidized powder and non-uniform distribution of powders on the rougher surface of L-PBFed-Layered compared to L-PBFed-Tracked. Moreover, owing to the difference in the laser absorption rate and cooling rate caused by the difference in surface roughness, the retained austenite fraction of the DEDed region appeared different. In particular, the DEDed region exhibited a higher retained austenite fraction because it had a higher content of austenite-stabilizing elements than the L-PBFed region; thus, the hardness decreased significantly. In some parts of the heat-affected zone, the hardness increased significantly because of aging effect. An impact test was performed to investigate the crack-propagation characteristics at the interface according to the relative building directions of DEDed and L-PBFed. Consequently, despite the interfacial defect at the interface of the DEDed and L-PBFed depositions, the resistance to cracking increased when the crack-propagation direction was perpendicular to the L-PBFed layer plane. However, even if there were no defects at the interface of the DEDed and L-PBFed parts, cracks progressed rapidly after a low plastic deformation in the specimen whose crack propagation direction was parallel to interlayer plane. This suggests that the characteristics at the DEDed/L-PBFed interface vary considerably depending on the relative building directions of the two metal AM processes.

在这项研究中，研究了通过混合金属增材制造 (AM) 工艺（激光粉末床融合 (L-PBFed) 和定向能量沉积 (DEDed)）沉积的材料的界面特性。分析了L-PBFed和DEDed不同相对构建方向下界面处的沉积特征、显微组织、结合性能和裂纹扩展特征。DED 的附加层沉积在由 L-PBFed 构建的基板的顶面（L-PBFed-Tracked 表面）和侧面（L-PBFed-Layered 表面）上。与 L-PBFed-Tracked 相比，L-PBFed-Layered 较粗糙表面上的粉末分布不均匀，导致在 DED 过程中 PBFed 和 DEDed 之间的界面处出现缺陷。而且，由于表面粗糙度不同导致的激光吸收率和冷却速度不同，DEDed区的残余奥氏体分数出现了不同。特别是，DEDed 区域的残余奥氏体分数更高，因为它的奥氏体稳定元素含量高于 L-PBFed 区域；因此，硬度显着下降。在热影响区的某些部位，由于时效作用，硬度显着增加。根据 DEDed 和 L-PBFed 的相对构建方向，进行了冲击试验以研究界面处的裂纹扩展特性。因此，尽管 DEDed 和 L-PBFed 沉积物的界面存在界面缺陷，当裂纹扩展方向垂直于 L-PBFed 层平面时，抗开裂性增加。然而，即使在 DEDed 和 L-PBFed 部件的界面处没有缺陷，在裂纹扩展方向平行于层间平面的试样中，在低塑性变形后裂纹迅速发展。这表明 DEDed/L-PBFed 界面处的特性因两种金属 AM 工艺的相对构建方向而有很大差异。