在拥有自主知识产权的TB-100选区激光熔化设备上制备316L不锈钢。通过金相显微镜对比研究了不同工艺参数(激光功率、扫描速度和扫描间距)下, 成形件的低倍缺陷, 主要为气泡、孔隙、微裂纹和宏观裂纹; 借助扫描电子显微镜和能谱仪, 研究了缺陷微观形貌特征和成分, 分析了各类缺陷形成机理。结果表明, 孔隙主要为圆气泡性孔隙、不规则形状工艺性孔隙和氧化物夹杂, 气泡主要为氢气泡和氮气泡, 而微裂纹主要为贯穿性孔隙以及内应力过大导致的热裂纹, 宏观裂纹主要为由于残余应力过大导致的层状裂纹, 属于冷裂纹。引入线能量密度(E＝P/v)为综合参数, 随着线能量密度的增大, 孔隙逐渐减少, 但是当线能量密度达到400 J/m时, 出现裂纹, 且大量出现气泡缺陷, 随着线能量密度的继续增大, 裂纹逐渐增多; 当线能量密度达到583 J/m时, 主要为裂纹缺陷, 气泡减少; 当线能量密度达到875 J/m时, 裂纹呈条状且尺寸明显增大, 裂纹与裂纹之间已相互连接。经分析测试验证, 316L不锈钢较优的工艺参数为激光功率190～210 kW, 激光扫描速度800～1 000 mm/s, 扫描间距0.90～0.11 mm, 此区间线能量密度200 J/m左右, 无裂纹, 基本无气泡, 存在少量孔隙, 产品致密度达99.7%。

316L stainless steel parts were manufactured on TB-100 selective laser melting equipment with independent intellectual property rights. The low-magnification defects of forming parts with different process parameters (laser power, scanning speed and scanning distance) were studied by metallographic microscope, mainly air bubbles, pores, microcracks and macrocracks. The formation mechanism of various kinds of defects were analyzed. the microstructure and composition of the defects were studied by means of SEM and EDS. The results show that the pores are mainly circular air pores, irregular process pores and oxide inclusions. The air bubbles are mainly hydrogen bubbles and nitrogen bubbles, while the microcracks are mainly caused by penetrating pores and thermal cracks caused by excessive internal stress, macrocracks are mainly the layer cracks caused by excessive residual stress, which belong to cold crack. Linear energy density (E＝P/v) is introduced as a synthetic parameter. As the line energy density increases, the pores decrease gradually. However, when the linear energy density reaches 400 J/m, cracks appear, and a large number of air bubbles defects appear. As the linear energy density continues to increase, the cracks increases gradually. When the linear energy density reaches 583 J/m, the defects were mainly cracks and bubbles decrease. When the linear energy density reaches 875 J/m, the cracks are strip-shaped and the size is significantly increased, and cracks are connected to each other. According to the analysis and test verification, the optimal process parameters of 316L stainless steel are laser power 190～210 kW, laser speed 800～1 000 mm/s and scanning interval 0.90～0.11 mm, and the linear energy density is about 200 J/m. There are no cracks, basically no bubbles, a small amount of pores, and the product density reaches 99.7%.