激光参数对旁轴送粉激光熔覆粉末熔化行为的影响

Effect of Laser Parameters on Melting Behavior of Powders in Off-Axis Laser Cladding Process

旁轴送粉激光熔覆时粉末到达熔池的热物状态对熔覆层成形精度和质量有着重要意义,针对光粉作用时粉末的不同熔化行为,搭建了旁轴送粉激光熔覆过程红外热成像采集系统和高速摄像过程采集系统,研究了不同激光功率和离焦量下的光粉热交互作用,建立了粉末熔化时出现的三个典型特征阶段并分析了不同激光功率和离焦量对粉末熔化特征阶段持续时间的影响,最终得出粉末热物状态与特征阶段的关系。结果表明:激光功率增大,光粉作用空间中熔化的粉末数量增多,粉末温度不均匀性减小;离焦量增大,液态粉末颗粒数量增大,粉末温度不均匀性横向减小;激光功率越小或离焦量越大,固态粉末升温和熔化所需的时间增大,粉末以固态进入熔池的几率变大。最后,得到了不同激光参数下粉末到达熔池时的热物状态,为实现粉末熔化行为的解析提供了试验依据。

The thermal state of powder arriving in a molten pool is crucial to the forming precision and quality of the cladding layer for off-axis laser cladding. Aiming at the different melting behavior of powder under the action of light powder, an infrared thermal imaging acquisition system and a high speed camera process acquisition system for the laser cladding process with off-axis powder feeding were built. The light powder thermal interaction under different laser powers and defocus amounts was studied. Three typical characteristic stages of powder melting were established. The influence of laser power and defocus amounts on the duration of the characteristic stage of powder melting was examined. Finally, the relationship between the thermal state of powder and characteristic stage was obtained. The findings depict that with the increase in laser power, the number of melted powder in the interaction space increases and the powder temperature uniformity decreases, and the number of liquid powder particles increases with an increase in defocus and the temperature inhomogeneity of powder decreases. The smaller the laser power or larger the defocusing amount, the time required for the temperature to rise and the solid powder’s melting increases. The powder’s probability of entering the molten pool in solid state increases. The thermal states of powder arriving at the molten pool under different laser parameters are obtained, providing an experimental basis for the powder melting behavior analysis.