Research On Bypass Coupling Twin-wire Indirect Arc Additive Manufacturing Process

As a novel welding process,the twin-wire indirect arc welding is characterized of high deposition efficiency,low heat input to the base metal and less deformation.Therefore,this technique is potentially advantageous in additive manufacturing.This thesis focused on the application of the bypass coupling twin-wire indirect arc welding for arc additive manufacturing and comparing it to the traditional MIG welding process.Firstly,the influence of the welding parameters on the droplet transfer and arc morphology was investigated.It was found that the welding current directly affected the droplet transfer.With the increase of anode wire feeding speed,the total welding current increased.In addition,the anode electrode wire changed from droplet transition to jet droplet transition,while the cathode welding wire was mainly large droplet transfer.The droplets formed respectively at the anode wire and the cathode wire presented a certain angle.The increase of the cathode wire feeding speed increased the indirect arc current and improved the stability of the angle.The bypass coupling twin-wire indirect arc welding was consisted of an indirect arc between the twin wires and a direct arc between the anode wire and the wire workpiece.The behavior of arc burning depended on the matching of the anode and cathode wire feeding speeds.Most of the time,the two arcs burned alternately,and occasionally presented simultaneous combustion.Under the same condition of welding current,compared to the traditional MIG welding additive manufacturing,the bypass coupling twin-wire indirect arc welding utilized for additive manufacturing improved the additive manufacturing efficiency.Meanwhile,the heat input and deformation of the substrate were significantly reduced.With the increase of cathode wire feeding speed,the efficiency of additive manufacturing increased more remarkably.The results of the research on the corrosion resistance of 18-8 stainless steel additive manufacturing products indicated:?The process stability of the bypass coupling twin-wire indirect arc additive manufacturing was improved with the increase of welding current.? The corrosion resistance of the additive manufacturing produced by bypass coupling twin-wire indirect arc welding was promoted with the increase of the welding current.Under the same total welding current condition,compared to traditional MIG welding additive manufacturing,the products manufactured by the bypass coupling twin-wire indirect arc welding not only achieved higher manufacturing efficiency,but also exhibited better intergranular corrosion resistance and pitting corrosion resistance.The mechanical properties of the additive manufactured components produced from the twin-wire indirect arc welding and the MIG welding were compared,which indicated:? Both the tensile strength and plasticity of the specimen obtained from these two different additive manufacturing methodologies were similar,.?The results of slow tensile stress corrosion demonstrated that the tensile strength of the 18-8 stainless steel products produced by the bypass coupling twin-wire indirect arc welding was significantly higher than that of MIG welding additive manufacturing.However,the slow tensile stress corrosion performance of 2520 stainless steel products obtained by these two additive manufacturing methods were basically similar.The fracture morphology of the additive manufacturing products by the two additive manufacturing methods were dimple-like,and therefore the fracture mode was ductile fracture.