Study On The Deposition Behavior And Experiment Of Laser Propelled Powder Forming

Laser additive remanufacturing technology is an advanced and green manufacturing technology,which can be used to realize the repair of key components in industrial equipment.It plays an important role in promoting the development of circular economy and environment-friendly society.The parts to be repaired are usually large in size,high in transportation cost and long in round-trip transportation cycle.They often need to be repaired on site.Most of the existing powder feeding laser additive remanufacturing technology appears powder escaping in the repair process,which will aggravate the loss in the operation process of the equipment.In order to solve the problem of powder dispersion in laser additive remanufacturing process.In this paper,a laser propulsion powder forming technology is proposed.The same path structure of the powder and light is adopted in the nozzle,and the air extraction device is connected under the nozzle.After the powder is fed into the nozzle from the side and pumped out through the air extraction port,the problem of powder escape can be effectively avoided.Through the research on the thrust of powder generated by laser,a prototype nozzle of powder forming by laser is developed.The main research results are as follows:(1)The nozzle of laser propulsion powder forming based on the same path of powder and light is designed.Firstly,the powder flow parallel to the horizontal plane of the substrate was observed by laser irradiation.The results show that when the laser energy density of the fiber laser is above 10~6 W/cm~2,the powder will overcome the resistance of the air flow and spray down.Then it is verified that the powder can flow in the same way nozzle without escaping.The powder can be pushed out of the nozzle by laser,and the molten pool can be formed on the substrate by laser which passing through the powder flow.The ejected powder is received by molten pool,and finally achieve effective deposition.(2)When laser irradiates the powder flow,the powder will be ejected from the air flow.The experimental results show that the thrust of powder increases with the increase of laser energy density.Compared with the powder without coating,the thrust of the coating powder can be increased to nearly ten times.Because the acceleration obtained by thrust is higher than the acceleration of gravity,the movement state of powder particles will change.At the same time,with the increase of particle diameter,the acceleration value decreases,and the movement state of small particle size powder is more susceptible to thrust.(3)The double laser beam is used to irradiate the powder flow parallel to the substrate movement.It is found that the advantage of semiconductor laser is that the large spot on the substrate is easy to form a stable molten pool after passing through the powder,while the optical fiber laser molten pool is limited.After two laser beams acting at the same time,the resistance of air flow can be overcome by the powder under the action of fiber laser.The result of effective deposition is achieved by the way that the powder enters the molten pool formed by semiconductor laser.(4)The air flow field of the light powder same path nozzle was observed by the fog steam tracing device.Through the test results,it is found that after the upper end is closed and the protective gas is introduced,the protective air flow suppresses the powder carrying air flow to rise,the air flow is opposed,and then enters the powder recovery device after stratification.When the powder circulates from the bottom to the top,the powder does not overflow,and when the laser is applied,the powder has a large amount of deposition on the surface of the substrate,and the deposition height can reach about hundreds of microns.In order to solve the problem of powder dispersion in the field of laser additive remanufacturing,the thrust and forming process of powder are systematically studies in the process of laser propulsion powder forming to realize the deposition and forming without powder overflow.The research results can provide theoretical support for the realization of laser additive manufacturing repair parts.