Study On The Process Characteristics Of Circular Multi-laser Melting Wire Additive Manufacturing

Space on-orbit additive manufacturing is an important modeling technique to support space manufacturing with its efficiency and flexibility,which can greatly reduce the cost of space exploration.Therefore,it is urgent to accelerate the development of this technology.Due to the limitation of space microgravity environment,it is proved that high energy beam fuse is a feasible technology for manufacturing metal materials on orbit in the future.Aiming at the problems such as the forming directionality caused by the side wire feeding in the additive manufacturing of metal wires,this paper is devoted to the development of additive manufacturing of ring-shaped multi-laser fuses,researching the forming process characteristics,and mastering the key process parameters for forming quality.Influencing laws,providing technical support for the development of metal wire additive manufacturing technology.In this paper,the Ti-6Al-4V alloy wire is used as the test material.In the vacuum environment,the forming of the cladding and thin-walled parts is mainly formed.The process characteristics and the microstructure properties are studied,and the process parameters are optimized.Based on this,the forming of the three typical samples is completed.For single cladding channel,the study shows that the circular multi-laser melting wire additive manufacturing technology has eliminated the influence of the directionality of the laser beam and achieves isotropicity.The scanning speed and laser power have great influence on the morphology and width to height ratio of the cladding channel.The ratio of width to height increases with the increase of scanning speed and laser power and the influence of wire feed speed and defocus amount is small.In single cladding channel,the structure is mostly acicular a' martensite.With the increase of scanning speed,the size of acicular a' decreases.With the increase of laser power and defocus,the grain size becomes larger.The speed of wire feeding has little effect on the microstructure.With the increase of the wire feeding speed,the hardness of the cladding channel decreases gradually,and the hardness of the cladding channel in the negative defocusing is obviously smaller than that in the positive defocusing mode.The scanning speed and the laser power have little effect on the hardness of the cladding channel.In the single-layer multi-channel forming,with the increase of the scanning distance,the maximum height of the unmelted gaps and contours of the claddings increases.There is a small needle at the junction of the cladding,and the hardness at the junction is significantly higher than the cladding channel.For the single channel thin-walled parts,the length of the thin-walled parts formed by the arch shaped scanning path is less lost.Thin-walled parts generally have a larger width of the first layer than the second layer.Starting from the second layer,the width of each layer first increases and then gradually keeps constant.The top microstructure of thin-walled is mainly elongated acicular a' martensite.The central part is mainly short rod-shaped ?-crossing formed basket structure;the bottom is mainly short rod-shaped ?-phase.The hardness is higher than that of other parts due to more a' phases on the top.The influence of increment and offset of z-axis on the forming of thin-walled parts was analyzed,and the appropriate parameters were determined.Based on the above studies,the optimized process parameters were selected,and the formation of three typical prototypes of box-shaped,cylindrical,and inclined cylindrical shapes was designed.By setting the rounding angle and the coincident angle,the problems such as the corners and the poor fusion between the head and the tail of the cladding are solved,the forming stability is improved,and the sample with good morphology is obtained.