采用水雾化316L不锈钢粉末, 开展选区激光熔化(SLM)成型工艺试验研究, 以期获得高致密度316L不锈钢试样。在层厚50 μm、点间距65 μm的条件下, 研究了激光功率、曝光时间、线间距对致密度的影响, 探讨了体能量密度对第一层表面粗糙度Ra及块体致密度的影响规律。研究结果表明, 单层试验表面粗糙度Ra随着体能量密度的增大而呈减小趋势, 当能量密度大于60.92 J/mm3时第一层表面粗糙度Ra保持在4 μm以下, 其中线间距对单层试验表面粗糙度Ra影响最明显, 随线间距的减小Ra值呈减小趋势; 成型件致密度随体能量密度的增大呈先增大后稳定趋势, 在激光功率200 W、曝光时间130 μs、线间距0.1 mm条件下获得相对致密度98.26%的试样; 能量密度较小导致层与层之间形成小孔、线间距太宽导致形成的间隙和热应力引起的裂纹是影响致密度最主要的原因。采用不同线间距成型, 得到抗拉强度593 MPa, 断后延伸率34.4%, 断面收缩率29.1%的拉伸样件。

Water-atomized 316L stainless steel powder has been employed to obtain 316L stainless steel parts with high density by selective laser melting. The effects of laser power, exposure time and hatch space on relative density and the influence of volume energy density on the surface roughness of the first layer and relative density of fabricated parts have been investigated on the condition of the layer thickness of 50 μm and dot space of 65 μm. The results show that the surface roughness of the first layer decreases with the increase of energy density. The surface roughness maintains less than 4μm as the volume energy density is larger than 60.92 J/mm3. Hatch space shows the most significant impact on surface roughness of the first layer, which decreases with the reduction of the hatch space. The relative density increases at first and then remains stable along with the increase of volume energy density. Bulk has been fabricated with the relative density of 98.26% under the condition of laser power of 200 W, exposure time of 130 μs and hatch space of 0.1 mm. The pores between layers due to low energy density, clearances resulted from large hatch space and cracks caused by thermal stress are the main reasons affecting the density of bulk. Tensile samples with tensile strength of 593 MPa, elongation percentage of 34.4% and area reduction percentage of 29.1% are obtained by optimizing the hatch space.