为了解决激光直接制造金属零件中同轴送粉喷嘴气体保护效果不佳的问题，采用烟雾流动显示技术对喷嘴保护气体流场进行了研究。系统研究了喷嘴保护气流速率、喷嘴出口距零件表面距离、喷嘴移动速率和侧风速率对气体保护效果的影响。结果表明，随着喷嘴保护气流速率的增加，保护范围先增加后减小；随着侧风速率和喷嘴移动速率的增大，气流轴线偏离喷嘴轴线距离增大；当侧风速率超过喷嘴气流速率50%，距喷嘴出口10mm处，气流完全偏离喷嘴轴线，完全失去对金属熔池的保护。这一结果为选择合适的喷嘴气流参量提供了依据。

In order to improve the shielding effect of gas flow field in laser direct manufacturing, the shielding gas flow field of coaxial powder feeder nozzles was studied by means of smoke flow visualization technology. The influence of gas velocity from nozzle, distance between parts and nozzle exit, moving velocity of nozzle and crosswind velocity on shielding gas field was investigated systematically. The results show that with the increase of gas velocity from nozzle, shielding effect increases at first and then gets worse; with the increase of velocity of crosswind and nozzle, the axis of shielding field and nozzle get apart; when the velocity of crosswind surpasses 50% of velocity of gas from nozzle, shielding field fails to protect molten pool totally at the place 10mm below the nozzle. The information can be used to select appropriate nozzle flow parameters.