一个包含了固体传热和层流的选区激光熔化(Selective Laser Melting, SLM)三维有限元模型被用来模拟选区激光熔化加工单层多道Inconel 718合金粉末的过程, 来预测加工过程中激光束的搭接率对成型质量的影响。为了提高模拟结果的准确性, 模型中考虑了激光在粉床中的穿透作用、粉床与实体热导率的明显差异、固液相变过程以及由于熔池表面存在温度梯度而引起的Marangoni对流。对Marangoni对流对熔池形貌的影响以及激光束搭接率对成型质量的影响进行了分析和讨论。结果显示, 加工过程中熔池内的熔融金属的对流为外向对流, 对流的存在使得熔池的深度减小、宽度增加。当激光束的搭接率为30%时, 工件内气孔较少, 加工质量较好。模拟结果与实验结果相对照, 吻合程度较好。

A three-dimensional finite element model of selective laser melting (SLM), which contains solid heat transfer and laminar flow, has been developed to simulate the laser melting process of single-layer multi-channel Inconel 718 alloy power to predict the effect of laser beam overlapping ratio on forming quality during processing. In order to improve the accuracy of the simulation results, the penetration of the laser in the powder bed, the significant difference in thermal conductivity between the powder bed and dense material, the solid-liquid phase transition process and the Marangoni convection due to the temperature gradient of molten pool surface are taken into account in the model. The effect of the Marangoni convection on the shape of the molten pool and the effect of laser beam overlapping ratio on the forming quality has been investigated in this paper. It shows that the convection of the molten metal in the molten pool during the process is outward convection, and the presence of convection causes the depth of the molten pool to decrease and increase the width. When the laser beam overlapping ratio is 30%, the number of pores in workpiece is obviously decreased, processing quality is better. The simulation results are in good agreement with the experimental results.