Distinguished by a marked combination of high strength and high fracture toughness, 18Ni-300 maraging steel (MS) is widely used for intricate tool and die applications. MS is also amenable to the powder bed fusion additive manufacturing process, providing unique opportunities to make small features and incorporate cooling channels in molds. In this study, tensile test samples were fabricated using selective laser melting to investigate the effects of built height and orientations on the evolution of the microstructure and the mechanical properties of the samples. The microstructure of the as-fabricated samples consists of the primary α-martensite phase and fine cellular microstructure (~0.66–0.83 μm) with the retained austenite γ-phase aggregated at the boundaries of the cells, resulting in an enhanced mechanical performance compared with traditional counterparts under the same condition (without post-heat treatments). Random grain orientations with weak textures are revealed in all samples. The XY-built samples display better tensile performance when compared to the Z-built samples due to the fine grain sizes and the retained γ phase. The bottom of the Z-built sample exhibits a higher hardness than other parts of the sample, which could be attributed to its finer cellular structure.

18Ni-300马氏体时效钢（MS）以高强度和高断裂韧性的显着组合而著称，被广泛用于复杂的工具和模具应用中。MS还适用于粉末床熔融添加剂的制造过程，为制造小型零件和在模具中整合冷却通道提供了独特的机会。在这项研究中，使用选择性激光熔化技术制备了拉伸测试样品，以研究建筑高度和方向对样品微观结构和机械性能的影响。加工后的样品的微观结构包括主要的α-马氏体相和精细的细胞微结构（约0.66-0.83μm），残余奥氏体γ相聚集在细胞边界，与在相同条件下（不进行后热处理）的传统同类产品相比，其机械性能得以提高。所有样品中均显示出质地较弱的随机晶粒取向。的XY相比时-内置样品显示更好的拉伸性能Ž -内置样品由于细晶粒尺寸和残留γ相。Z型样品的底部比其他部分具有更高的硬度，这可能归因于其更精细的孔结构。