Optimization Of Laser 3D Printing Of Coaxial Stream Parameters And Characteristics Analysis Of Laser Plasma

This paper mainly focused on the process of the laser 3D printing with coaxial powder flow.In this paper,the optimization design method of powder feeding parameters and laser parameters was studied,the characteristics of laser plasma in 3D printing manufacturing process was analyzed,and the effect of powder on Laser Plasma was investigated.The main work is as follows:The laser 3D printing with coaxial powder flow processing system,the laser plasma charge signal acquisition system and the laser plasma image signal detection system was designed and established.For the powder feeding parameters and laser parameters involved in the laser 3D printing with coaxial powder flow,image analysis,sediment layer analysis,and other methods are used to perform parameter optimization via regression analysis,comparative analysis.By analyzing the charge signal and the image signal,as well as the evolution characteristics of the laser plasma which generated in the laser 3D printing with coaxial powder flow,the influence of the powder flow on the laser plasma during the processing and the variation of the laser plasma when the powder feed parameters and the laser parameters are changed are studied.The results show that the best combination of parameters for the laser 3D printing with coaxial powder flow is:carrying gas flow 4L·min^-1,assisting gas flow 17L·min^-1,laser peak power 6kw,laser pulse width 4.5ms and defocusing distance 8mm,the parameter combination can be used to obtain the best deposition layer shape.By analyzing the eruption characteristics of laser plasma,it is proposed that the laser plasma eruption mode can be divided into a stable eruption mode and an unstable eruption mode.The unstable eruption mode can be divided into secondary wave mode and inhomogeneous main wave mode.By comparing the charge signal and electron temperature signal of the laser plasma with powder flow and without powder flow,it is proposed that the presence of the powder flow enhances the eruption intensity of the laser plasma and shortens the eruption duration of the laser plasma.By changing the powder feeding parameters and laser parameters,it is found that the electron temperature and eruption duration of the laser plasma increases with the increase of the carrying gas,increases with the increase of assisting gas,and increases first and then decreases with the increase of amount of powder feeding,it is also found that the electron temperature of the laser plasma increases first and then decreases with the increase of the scanning speed,decreases first and then increases with the increase of the frequency of the laser pulse,and then rapidly increases and then tends to be stable with the increase of the laser pulse width.As the plasma eruption intensity and duration increase,the absorption of laser energy by the deposited layer and powder flow will be affected,thereby affecting the laser deposition efficiency and quality of 3D printing.