The usage of high laser power is one of the popular strategies to improve the productivity of selective laser melting technology. Herein, the single-track, single-layer and bulk 300M steel specimens were produced by high power selective laser melting (HP-SLM) to investigate the defects, densification mechanism, microstructure, tensile properties and impact toughnesses of HP-SLMed 300M steel parts. The results show that three main types of defects including protrusions, depressions and spatters exist on the surfaces of the prior solidified layers during the HP-SLM depositing process. The flexible powder laying strategy such as a soft scraper can be used to eliminate the instability of the powder-spreading process caused by the protrusions and spatters. Besides, the 300M steel parts with a relative density of more than 99.9% can be printed via the combined usages of high laser power (2000 W) and low scanning speed (400 mm/s) with a soft scraper. Meanwhile, the theoretical depositing rate for the HP-SLM process can reach 17.28 mm³/s. The as-printed 300M steel specimens exhibit the heterogeneous microstructure with the spatial alternating stacks of low-temperature tempered martensite and high-temperature tempered martensite. Too large hatch spacing (≥ 220 µm) can make the tensile properties of HP-SLMed parts degraded dramatically due to the unfused powders and unfused spatters. However, the tensile properties of the as-printed parts vary marginally as the layer thickness varies from 120 µm to 180 µm. The tensile strength (~1217 MPa) and elongation (~12.65%) of the vertical specimens are higher than those (~1149 MPa, 11.80%) of the horizontal specimens while the yield strength (~1058 MPa) of the vertical specimens is lower than that (~1120 MPa) of the horizontal specimens. Additionally, the impact toughness (96.5 J/cm²) of HP-SLMed 300M steel parts is much superior to that of weldments and forgings.

高激光功率的使用是提高选择性激光熔化技术生产率的流行策略之一。在此，通过高功率选择性激光熔化（HP-SLM）生产单轨道，单层和散装的300M钢试样，以研究HP-SLM加工的300M钢零件的缺陷，致密化机理，显微组织，拉伸性能和冲击韧性。 。结果表明，在HP-SLM沉积过程中，先前固化层的表面上存在三种主要类型的缺陷，包括凸起，凹陷和飞溅。可以使用诸如软刮刀之类的柔性粉末铺设策略来消除由突起和飞溅引起的粉末铺展过程的不稳定性。此外，300M钢零件的相对密度大于99。结合使用高激光功率（2000 W）和低扫描速度（400 mm / s）并使用软刮刀，可以打印9％的纸张。同时，HP-SLM工艺的理论沉积速率可达到17.28 mm³ /秒 印刷后的300M钢试样显示出不同的微观结构，其中低温回火马氏体和高温回火马氏体在空间上交替堆叠。舱口间距太大（≥220 µm）会使未固溶的粉末和未固结的飞溅物导致HP-SLM零件的拉伸性能急剧下降。但是，随着层厚从120 µm到180 µm的变化，印刷部分的拉伸性能略有变化。垂直样品的抗拉强度（〜1217 MPa）和伸长率（〜12.65％）高于水平样品的抗拉强度（〜1149 MPa，11.80％），而垂直样品的屈服强度（〜1058 MPa）较低比水平试样的应力（〜1120 MPa）高。此外，冲击韧性（96.5 J / cm ²）HP-SLMed 300M钢零件的焊接性能远优于焊件和锻件。