The M789 steel was designed by voestalpine group based on Grade 250 maraging steel to maintain good printability and increase the corrosion resistance. In this work, the M789 steel was manufactured by laser powder bed fusion process. The microstructural evolution of additively manufactured M789 steel was studied using optical and electron microscopy techniques. In the as-printed condition, the epitaxial grain growth with cellular dendritic structure was detected. The primary dendrite arm spacing was measured to be 0.42 ± 0.12 μm, suggesting the cooling rate is in order of 10⁶ °C/s during solidification. This high cooling rate eliminates the occurrence of precipitation. The electron backscatter diffraction maps indicate the formation of elongated columnar grains with significant low-angle grain boundaries. After solution annealing and aging treatment, large needle-like martensitic structures were observed with fewer LAGBs than the as-printed condition. Spherical ETA-Ni₃(Ti,Al) precipitates (η-phase) were formed during the heat treatment, leading to a significant increase in hardness, tensile strength, and yield strength compared to the as-printed condition. The tensile strength and yield strength along the building direction are 1798 ± 4 and 1714 ± 13 MPa, respectively. However, the elongation and toughness in the heat-treated condition are lower than that of the as-printed condition. Thermodynamic and mechanical properties simulations were also carried out, and the results are consistent with the experimental data.

奥钢联集团基于250级马氏体时效钢设计了M789钢，以保持良好的适印性并提高耐腐蚀性。在这项工作中，M789钢是通过激光粉末床熔融工艺制造的。使用光学和电子显微镜技术研究了增材制造的M789钢的组织演变。在印刷条件下，检测到具有细胞树突结构的外延晶粒生长。初次枝晶臂间距经测量为0.42±0.12μm，表明冷却速率约为10 ⁶固化期间的°C / s。如此高的冷却速度消除了沉淀的发生。电子背散射衍射图表明具有明显的低角度晶界的细长柱状晶粒的形成。经过固溶退火和时效处理后，观察到大针状马氏体组织，其LAGBs少于印刷条件。球形ETA-Ni ₃（Ti，Al）析出物（η-相）在热处理过程中形成，与印刷条件相比，导致硬度，抗张强度和屈服强度显着提高。沿建筑方向的抗拉强度和屈服强度分别为1798±4和1714±13 MPa。然而，在热处理条件下的伸长率和韧性低于印刷条件下的伸长率和韧性。还进行了热力学和力学性能模拟，结果与实验数据一致。