Directed energy deposition (DED) is a mainstream metal additive manufacturing technique that can fabricate near-net-shape components and repair damaged parts with a high build rate. Monel K-500 is a Ni-based alloy widely used for marine and offshore applications because of its excellent corrosion resistance and good combination of strength and ductility. In this study, laser-assisted DED (L-DED) was used to print Monel K-500 parts from powder. The key process parameters, including the laser power and scanning speed, were optimized to obtain single beads with desirable geometry and blocks with nearly full density (≥99%). The block samples printed by L-DED exhibit ∼20% higher ultimate tensile strength and ∼60% higher elongation to failure than their conventional cast counterparts. From the microstructure examination, it is found that the parts printed with a low laser power have fine grains and an alternating equiaxed/columnar-grain sandwich structure with high tensile strength. In contrast, those printed with a high laser power have coarse columnar grains with a strong <001> texture but low tensile strength. The mechanism accounting for the grain structure evolution was studied by computational fluid dynamics and cellular automata simulations. The anisotropy in mechanical properties is mainly attributed to the difference in grain boundary strengthening effects. Moreover, the increase in hardness and tensile strength of the heat-treated samples is attributed to the precipitation hardening effect. This work exemplifies how the process parameters can be tuned to control the grain texture to achieve superior mechanical properties for parts of Monel K-500 and other metals printed by L-DED.

定向能量沉积 (DED) 是一种主流的金属增材制造技术，可以制造近净形部件并以高构建率修复受损部件。Monel K-500 是一种镍基合金，由于其优异的耐腐蚀性和良好的强度和延展性，广泛用于船舶和海上应用。在这项研究中，激光辅助 DED (L-DED) 用于从粉末打印 Monel K-500 零件。优化关键工艺参数，包括激光功率和扫描速度，以获得具有理想几何形状的单个珠子和几乎全密度 (≥99%) 的块。由 L-DED 打印的块状样品与传统的铸件样品相比，其极限抗拉强度高 20%，断裂伸长率高 60%。从显微组织检查来看，发现用低激光功率打印的零件具有细晶粒和交替的等轴/柱状晶粒夹层结构，具有较高的抗拉强度。相比之下，用高激光功率打印的那些具有粗大的柱状晶粒，具有强 <001> 纹理但抗拉强度低。通过计算流体动力学和元胞自动机模拟研究了解释晶粒结构演变的机制。力学性能的各向异性主要归因于晶界强化效应的差异。此外，热处理样品的硬度和抗拉强度的增加归因于沉淀硬化效应。