High power selective laser melting (HP-SLM) has been used to manufacture the 300M steel single tracks. The influences of laser power and layer thickness on the formability, microstructure and mechanical properties of single tracks were researched. The results show that the optimized parameter window for HP-SLM of 300M steel is determined as laser power 500–1800 W, scanning velocity 400–600 mm/s, layer thickness 80–160 μm. Laser power has a great influence but layer thickness has little effect on the shape and mode of the molten pool (MP). The microstructure of SLMed 300M steel presents an epitaxial growth of columnar crystals and mainly consists of lath α' martensites with no obvious element micro-segregation. Laser power has little effect on the morphology but a great influence on the size and misorientation of the microstructure. However, layer thickness has little effect on the morphology and size but significant influence on the misorientation of the microstructure. The average microhardness increases firstly (~453 to ~551 HV) and then decreases (~551 to ~533 HV) when laser power varies from 500 to 2000 W. However, the average microhardness nearly remains constant (~530 HV) when layer thickness varies from 80 to 200 μm.

高功率选择性激光熔化（HP-SLM）已用于制造300M钢单轨。研究了激光功率和层厚对单道成形性，微观组织和力学性能的影响。结果表明，确定300M钢HP-SLM的最佳参数窗口为激光功率500-1800 W，扫描速度400-600 mm / s，层厚度80-160μm。激光功率影响很大，但是层厚对熔池（MP）的形状和模式影响很小。SLMed 300M钢的显微组织呈现出柱状晶体的外延生长，主要由板条α'马氏体组成，没有明显的元素微偏析。激光功率对形态几乎没有影响，但对微结构的尺寸和取向错误影响很大。然而，层厚对形态和尺寸影响很小，但对微结构的取向错误影响很大。当激光功率从500到2000 W变化时，平均显微硬度首先增加（〜453至〜551 HV），然后降低（〜551至〜533 HV）。但是，当层厚时，平均显微硬度几乎保持恒定（〜530 HV）。从80到200μm不等