The performance of the selective laser melting (SLM) parts was critically affected by the surface quality and internal defects that are closely related to process parameters. An in-depth understanding of the relationship between the formation and evolution of surface and internal defects and process parameters is needed to achieve defect-free and high-performance SLM parts. In this study, the influencing mechanism of laser power, scanning speed, hatch spacing and layer thickness on melt pool morphology, surface quality and internal hole defect of SLMed 18Ni300 maraging steel was investigated. The thermal and physical behaviour and instability of the molten pool, as well as the formation and distribution behaviour of internal hole defects, were also analyzed and discussed. Recoil pressure, the insufficient overlap between tracks and remelting between layers, Plateau-Rayleigh instability and material aggregation caused by the Marangoni effect were characterized as the main factors closely related to molten pool morphology and surface quality. Within the selected parameters in this study, the obtained surface roughness and tensile strength range from 9.08–26.40 μm and 544.14–1246.24 MPa, respectively. The internal defect changes from irregular lack-of-fusion at low energy density to the keyhole-included spherical hole at high energy density. In addition, the volumetric energy density (VED) has a certain limitation in predicting surface quality and mechanical properties due to the complex physical characteristics of the molten pool.

选择性激光熔化 (SLM) 零件的性能受到与工艺参数密切相关的表面质量和内部缺陷的严重影响。需要深入了解表面和内部缺陷的形成和演变与工艺参数之间的关系，以实现无缺陷和高性能的 SLM 部件。本研究研究了激光功率、扫描速度、舱口间距和层厚对SLMed 18Ni300马氏体时效钢熔池形貌、表面质量和内孔缺陷的影响机制。还分析和讨论了熔池的热和物理行为和不稳定性，以及内孔缺陷的形成和分布行为。反冲压力，轨迹重叠不足、层间重熔、高原-瑞利不稳定性和马兰戈尼效应引起的物质聚集被表征为与熔池形态和表面质量密切相关的主要因素。在本研究中选择的参数内，获得的表面粗糙度和拉伸强度范围分别为 9.08-26.40 μm 和 544.14-1246.24 MPa。内部缺陷从低能量密度下的不规则未融合转变为高能量密度下包含锁孔的球形孔。此外，由于熔池的复杂物理特性，体积能量密度（VED）在预测表面质量和力学性能方面具有一定的局限性。马兰戈尼效应引起的高原-瑞利不稳定性和材料聚集被表征为与熔池形态和表面质量密切相关的主要因素。在本研究中选择的参数内，获得的表面粗糙度和拉伸强度范围分别为 9.08-26.40 μm 和 544.14-1246.24 MPa。内部缺陷从低能量密度下的不规则未融合转变为高能量密度下包含锁孔的球形孔。此外，由于熔池的复杂物理特性，体积能量密度（VED）在预测表面质量和力学性能方面具有一定的局限性。马兰戈尼效应引起的高原-瑞利不稳定性和材料聚集被表征为与熔池形态和表面质量密切相关的主要因素。在本研究中选择的参数内，获得的表面粗糙度和抗拉强度范围分别为 9.08-26.40 μm 和 544.14-1246.24 MPa。内部缺陷从低能量密度下的不规则未融合转变为高能量密度下包含锁孔的球形孔。此外，由于熔池的复杂物理特性，体积能量密度（VED）在预测表面质量和力学性能方面具有一定的局限性。获得的表面粗糙度和拉伸强度范围分别为 9.08-26.40 μm 和 544.14-1246.24 MPa。内部缺陷从低能量密度下的不规则未融合转变为高能量密度下包含锁孔的球形孔。此外，由于熔池的复杂物理特性，体积能量密度（VED）在预测表面质量和力学性能方面具有一定的局限性。获得的表面粗糙度和拉伸强度范围分别为 9.08-26.40 μm 和 544.14-1246.24 MPa。内部缺陷从低能量密度下的不规则未融合转变为高能量密度下包含锁孔的球形孔。此外，由于熔池的复杂物理特性，体积能量密度（VED）在预测表面质量和力学性能方面具有一定的局限性。