同轴送粉激光成形中粉末与激光的相互作用

Interaction of the Laser Beam and the Metal Powder Conveyed by Coaxial Powder Feeder

详细介绍了同轴送粉激光成形过程中,金属粉末与激光束相互作用时间的计算方法。在ANSYS软件平台上,建立了金属粉末穿越激光束过程中粉末温度场的计算模型。系统计算了不同颗粒大小316L不锈钢粉末与不同功率激光束相互作用后的温度。在此基础上,计算了金属粉末与激光束的能量交换及金属粉末落入激光熔池后与激光熔池的能量交换。计算结果表明,在激光束直径为3 mm条件下,316L不锈钢粉末穿过功率大于1000 W的激光束后,所有尺寸金属粉末均被熔化,即金属粉末以液态进入激光熔池。通过金属粉末与激光束及激光熔池的能量交换计算,可知在激光成形中,约有5%的激光能量用于加热和熔化粉末,而大约95%的激光能量用于激光熔池的形成及由于热传导造成的热量损失。

A method to calculate the interaction time between metal powder and laser beam during laser direct forming with the metal powder conveyed by coaxial powder feeder is introduced in detailed. A finite element method (FEM) model based on ANSYS software is established to calculate the temperature of the metal powder while it crosses through the laser beam. Under different laser power condition, after interaction with laser beam, the temperature of the 316 L stainless steel (SS) powder of different size is calculated. Thus the laser energy absorbed from laser beam by metal powders is calculated. After 316 L SS powders have entered laser molten pool, the energy exchange between laser molten pool and 316 L SS powders is also calculated. The calculated results show that all 316 L SS powders are melted after they have crossed through the laser beam with power larger than 1000 W. It is to say that the 316 L stainless steel powders are turned from solid into liquid before they reach the surface of laser molten pool. The calculated results also show that during laser direct forming, approximately 5% of laser energy is used to heat and melt metal powders and 95% of laser energy is used to form laser molten pool and to compensate the heat loss due to thermal conduction.