Study On Key Technologies For Fabricating High Performance Metal Components By Multi-Arc Collaboration Additive Manufacturing

In the fields of naval-vessel and aerospace,there are many high-performance metal components with complex structure,large size,and high performance and accuracy requirements.The wire arc additive manufacturing technology is an effective method for forming such metal components.In order to realize the high efficiency and quality forming of high performance metal components by additive manufacturing,the following aspects of researches have been systematically studied in this paper:the design and integration of additive manufacturing equipment,the forming behavior of multi-wire additive manufacturing,the multi-arc additive manufacturing deposition process parameters optimization and microstructure control,the path planning and accuracy control method of multi-arc additive manufacturing.Finally,the marine propeller,propeller bracket and rocket macine conical shell components were fabricated with high quality.The main conclusions can be drawn as following:（1）The high efficiency multi-arc collaborative additive manufacturing equipment was integrated,including additive manufacturing unit,three-dimensional measurement unit,maching unit and control unit.The developed additive manufacturing unit coordinated two single-wire contour arcs and single-power triple-wire swing filling arcs.Among them,two contour arcs ensured the forming accuracy,and single-power triple-wire oscillating arc ensured the forming efficiency.The 3D measuring unit utilized 3D measuring instrument to evaluate dimensional accuracy,and the machining unit used high frequency dynamic spindle for surface processing.And the process monitoring device was integrated to realize the monitoring of process parameters and molten pool size during multi-arc additive manufacturing.The equipment not only showed high forming quality,but also realized forming efficiency of 1800 cm³/h.（2）The formation mechanism of co-droplet in single-power triple-wire oscillating arc was studied.It was found that the co-droplet was very stable under the action of electromagnetic force and surface tension,which could ensure the stability of droplet during its transfer.With the increase of process parameters,the droplet transition forms successively showed rejection transition,submerged arc transition,particle transition and ejection transition.At the same time,the cross-section morphology of triple-wire deposition layer under different swing modes was analyzed.The deposition layer cross-section of triangular swing was parabolic,resulting in highest flatness.The variation law of temperature field and dynamic strain of multi-arc additive was explored.It was found that the molten pool of contour arc and filled arc synchronously solidified during the multi-arc additive manufacturing.The filled arc uniformly heated the inside and outside of the component to make temperature field uniform,which greatly reduced the strain and stress of the parts.（3）The multi-arc synergistic additive manufacturing motion model and process window were established.When the relationship between the robot forward velocity V_Y,the deposition layer width D and the swing velocity V_X satisfied the relationship shown as （?）,the deposition layer with well forming.The multi-arc additive manufacturing process window as follows:the contour arc current of 70～90 A,the filling arc current of580～620 A,the stacking width of 80～130 mm,the filling arc gun swing speed of 12～14 mm/s.The thermal cycle characteristics of multi-arc additive manufacturing with different horizontal space were compared.It was found that the peak temperature and T_8/5of thermal cycle could be changed by adjusting the horizontal space of contour and filling arc,realizing control of microstructure and performance of components.The microstructure evolution law of multi-arc synergistic additive manufacturing components was studied.It was found that the deposited metal experienced solidification zone,coarse grain zone,normalizing zone and finally evolved into stable zone.（4）A model partition strategy based on unique normal vector was proposed,which divided high-performance metal components into cylinder,cone,nonlinear body,variable cross-section body and intersecting region partition to form with a single normal vector.The cylindrical slice was used to discretely stratify the variable cross-section body and the intersecting area to ensure the continuity of the printing path.A multi-arc cooperative path planning method was established for forming thin-wall regions in large metal components.The multi-arc variable attitude swing filling methods adjusts the attitude of machine head forming equal thickness area according to the printing path in real time.The multi-arc variable thickness swing filling method changes the swing amplitude simultaneously according to the printing profile to form the deformation thickness area.Finally,the multi-arc additive manufacturing components precision control method was established based on the offset of deposition layer cross-section center,which improved the forming accuracy in real time.（5）Three typical high-performance metal components were manufactured by the developed additive manufacturing equipment.The propeller components with space curved blades was formed with size error is within±1.6 mm.The tensile strength and impact power were repectively increased by 8.2%and 30%compared with the casting propeller.The conical shell component of rocket engine with variable cross-section was fabricated by wire swing-arc additive manufacturing with the maximum roundness of cross-section of±0.31 mm and the overall forming accuracy of±0.625 mm.The tensile strength and impact power were respectively increases by more than 1.6%and 8.8%compared with the welded shell.The marine propeller bracket with arm length of 3.5 m was manufactured by multi-arc collaborative additive manufacturing with forming accuracy of±0.6 mm.The tensile strength is increased by 18.9%,the impact power is increased by 29.8%and the forming efficiency was increased by about 4.7 times compared with the single-arc additive manufacturing component.