Research On Energy Directional Transmission Mechanism Of Laser Induced Arc In Additive Manufacturing

When the arc is used as a single heat source for metal additive manufacturing,because of the poor stability of the arc and the poor controllability of the molten pool,it is prone to defects such as molten metal overflow and collapse of the deposition structure,which will affect the forming quality of the additive manufacturing components.The hybrid heat source formed by laser induced arc combines the advantages of laser and arc to make up for the shortcomings in the arc additive manufacturing process.However,the lack of understanding of the mechanism of laser induced arc energy transfer has limited the application of the hybrid heat source in the actual additive manufacturing process.In this thesis,a laser induced arc additive manufacturing experimental system is established for aluminum alloy materials.The characteristic information such as electrical signal and arc shape in the additive manufacturing process are collected synchronously.The influence of laser on the form of arc droplet transfer is studied.The characteristics of electron temperature and electron density of laser induced arc coupled plasma are analyzed.Finally,the laser induced arc energy directional transmission mechanism is discussed.The results show that when the laser induces non-pulsating MIG arc,the short-circuit transition frequency is lower than that of single arc,but the arc electric signal waveform is more uniform.When laser induced pulsed MIG arc,it was found that laser energy can reduce the occurrence of unstable droplet short-circuit phenomenon,and with the increase of laser power,this unstable droplet transition phenomenon is effectively suppressed.At the same time,the surface forming quality of the deposition layer has been improved to a certain extent.By calculating the physical parameters of the laser induced arc coupled plasma,it is found that the coupled plasma electron temperature is larger than the single arc when the arc power is small.When the arc power is increased to a certain extent,the coupled plasma electron temperature does not change significantly.In addition,by changing the pulsed laser output energy,it is found that the coupled plasma electron temperature and electron density number increase as the laser peak power increases.When the single pulse energy of laser is fixed,both the electron temperature and the electron density decrease as the laser pulse width increases.By changing the heat source spacing,it is found that the coupled plasma electron temperature and electron density number increase first and then decrease as the heat source spacing increases.Through high-speed camera and synchronous acquisition of electrical signals,it is found that the addition of laser can improve the possibility of a successful arc arcing,and significantly change the direction of arc energy transmission during the action of pulsed laser.The arc root is partial to the laser action point and the arc conductive channel is compressed to a certain extent,which shows the directional characteristics of arc energy transmission.Finally,the laser induced arc physical conduction model is established by studying the directionality of laser induced arc energy transfer and the characteristics of coupled plasma physical parameters.It is believed that the fundamental reason for the laser induced arc energy directional transmission is that the laser energy destroys the oxide film on the surface of the metal base material to provide a stable cathode spot for the arc,and the charged particles in the laser induced plasma participate in the arc conduction,which makes the arc combustion more stable.