Research On Fabrication Process And Characteristics Of Water-bath Gas Tungsten Arc Additive Manufacturing

In this paper,aiming at the problem of accumulation of deformation of weldment and substrate in the process of additive manufacturing of GTA,a GTA additive process of water bath was proposed.The principle and system composition of GTA additive process in water bath were described.The cladding rate,substrate deformation and forming quality of additive GTA process in water bath and air cooling process were contrasted.Single-layer single-pass orthogonal experiment was designed and the influence of the three main process parameters of the covering current,deposition speed and wire feeding speed on the melting width and residual height of single-pass weld was studied.The relationship between the process parameters and the appearance and size of the straight wall,the microstructure and composition,mechanical properties and other aspects of the impact of in-depth study.Finally,the complex path interlaced structural elements were designed and shaped,and water bath GTA additive system and technology was to further optimization.Firstly,the deposition rate,substrate deformation and forming quality of additive manufacturing under water bath and air cooling conditions were compared.The results showed that the deposition rate under water bath condition was stable at 144g/h,which was 2.7 times of that under air cooling condition.The substrate flatness was 2.114 in water bath and 24%lower than air-cooling.The water bath had a great influence on the forming accuracy of the straight wall in the height direction and had little effect on the width direction.The height standard deviation of the straight wall forming part in the water bath was 2.6,lower than the air cooling(3.1)and 0.3 in the width direction.Then,the single-pass and multi-pass single-wall straight wall processes of GTA-AM were studied.The results showed that the influence order of the different process parameters on the weld width was:deposition speed>covering current>wire feeding speed;The velocity and the melting width were approximately proportional to each other.The current in the covering layer,the wire feeding speed and the melting width were approximately inversely proportional.The influence of different process parameters on the weld residual height was as follows:wire feed speed>deposition speed>covering current;wire feed speed and residual height were approximately proportional,covering current,deposition speed and melt width were approximately inversely proportional relationship.With the increase of heat input,the width of straight wall increases;with the increase of wire feeding speed,the height of straight wall monolayer increases.Straight wall of the first few layers due to the cooling speed,leading to the formation of narrow and high profile.Finally,the influence of three main process parameters(the covering current,the deposition speed,the speed of wire feeding)and the cooling conditions of water bath and air-cooling on the microstructure,tensile strength and microhardness of the straight wall were studied.The results showed that the microstructure of the ER316L stainless steel additive-shaped straight-walled body mainly consisted of columnar dendrites.The microstructure of the straight-wall body of the additive-shaped body in the height direction consisted of fine cell-like crystals? cellular dendrites? dendrites? Axial transformation,and the grain size gradually increased.With the change of the technological parameters of the water bath additive,the dendrite morphology and the dendrite spacing in the formed straight wall member have obviously changed.High deposition speed,small current and fast wire feeding speed can be obtained for smaller grain size,and then get more good mechanical properties.The microstructure,microhardness and tensile strength of straight wall members under water and air cooling were compared.The microstructure of the water bath was more fine and the microhardness was higher in both sides of the thickness direction of straight wall.,There is no change in size of the microstructure in the central area,and the tensile strength of the two is comparable.