激光功率与底面状态对选区激光熔化球化的影响

Influence of laser power and surface condition on balling behavior in selective laser melting

为研究激光功率与底面状态对选区激光熔化熔池流动的影响,基于离散单元法建立了选区激光熔化铺粉模型,采用粒径分布与实验相符的马氏体时效钢粉末分别铺展到平坦底面和增材底面上,将计算获得的粉末分布导入到基于有限体积法建立的选区激光熔化熔池计算流体力学模型中,研究激光功率和基板底面粗糙度对熔池流动和熔道表面形貌的影响。采用激光单道扫描实验验证铺粉模型和选区激光熔化模型。结果表明:随着激光功率的降低,单位长度的球化数量增加;由于增材底面使熔池润湿性变差,同时又对熔池流动行为产生扰动,使得增材粗糙底面上熔道的球化数量增加。选区激光熔化铺粉模拟及激光单道扫描模拟结果与实验结果吻合较好。本研究可为选区激光熔化工艺中工艺参数的选择提供理论指导。

This study proposes a Powder Spreading(PS)model and a Computational Fluid Dynamics(CFD)model to investigate the influence of laser power and surface condition on balling behavior for Selective Laser Melting(SLM).Metal powders are spread on a flat surface and an as-built surface.The simulated powder bed is then imported into a molten pool of the SLM-CFD model based on the finite volume method.The effect of laser power and substrate surface condition on the flow behavior of the molten pool and induced single track morphology are studied.To verify the PS and SLM-CFD models on both substrate surfaces,an SLM experiment is also conducted.The results show that the balling number decreases with the increase of laser power.Due to the poor wettability and disturbance in the molten pool induced by the as-built surface,the balling behavior on the as-built surface becomes more serious.The simulated results has a good agreement with experimental results.The study provides a theoretical guide to the selection of the processing parameters for SLM processes.