Processing Characteristics,Macro/microstructure And Mechanical Properties Of GH4169 By CMT Arc Additive Manufacturing

The Wire Arc Additive Manufacturing technology is an additive manufacturing technology with the main technical features of simultaneous feeding and feeding of wire materials.This technology can realize unsupported,fast and digital rapid forming of large and medium-sized metal components,and is more suitable for modern manufacturing technology.Complex,efficient,and flexible features.The Wire Arc Additive Manufacturing technology and the traditional processing technology such as casting,forging,turning and milling have different forming principles.The physical and chemical metallurgical reaction process of the material is more complicated.The deposition and forming of the wire and the change of the alloy structure under the action of the arc Lack of clear understanding.The research on the forming characteristics and microstructure properties of GH4169 superalloy produced by CMT arc additive is helpful to deepen the forming control of GH4169 superalloy in the process of arc additive manufacturing and the understanding of microstructure evolution and mechanical properties.The forming of single cladding layer was studied by using CMT welding machine's "non-unitary function",the short-circuit current duration and the short-circuit current in the CMT current waveform have a great influence on the spreadability of the cladding layer,and the wettability of the cladding layer and the substrate is poor in the CMT mode.On this basis,we further explored the influence of process parameters on the formation of cladding layer in CMT mode and CMT+Pulse mode.The higher the welding speed in CMT mode,the higher the wire feeding speed,the worse the spreadability of the cladding layer;CMT In +Pulse mode,the larger welding speed,wire feeding speed,and the better the spreadability of the cladding layer.Experiments show that the spreadability of single cladding layer is better than that of single cladding layer,the higher the temperature,the better the spreadability of the cladding layer.When the substrate preheating temperature is increased from 100 ° C to 400 ° C,the width of the cladding layer is increased by about 2 mm.The smaller the dry elongation of the wire,the greater the power density of the arc acting on the substrate,and the more favorable the spreading of the cladding layer.When the wire dry elongation is reduced from 10.5 mm to 6.5 mm,the arc height is reduced,and the cladding layer is reduced.The width is increased by about 1.1 mm.When the dry elongation of the wire continues to decrease to 5 mm,the area of the bottom of the arc acting on the molten pool is reduced,and the width of the cladding layer is decreased.The thin-walled layer-by-layer forming test shows that,when the number of forming layers is large,the heat accumulation at the top of the cladding layer is large,and the overlap between the layers of the cladding layer and the layer is large,forming a thin wall.The uniformity is reduced.In the layer-by-layer deposition process of thin-wall forming,the boundary shape of the cladding layer is mainly affected by the forming temperature and the dry elongation of the wire.The dry elongation of the wire is constant.When the forming temperature is low,the shape of the cladding layer is relatively symmetrical and uniform.The surface quality of the formed thin wall is better,the forming error is less than 0.2 mm;the dry elongation of the wire is constant,and the forming temperature is higher.The larger the coating width is,the smaller the height is,and the shape of the cladding layer is different.The melting amount of each cladding layer under the arc is higher at higher temperature,and the melting amount of the maximum cladding layer is about 66%.Microstructure analysis showed that,the microstructure evolution of CMT arc forming GH6169 alloy is mainly represented by the growth direction of columnar crystals,the spacing of primary dendrite arms and Laves phase,and the as-deposited microstructure of epitaxially grown columnar crystals.The heat dissipation direction of the formed thin wall is mainly along the deposition direction,and the coarse columnar crystal penetrates the entire cladding layer.The higher the number of deposited layers,the larger the inter-dendritic arm,the more obvious the orientation characteristics of the Laves phase,and the one interdendritic arm The maximum thickness is about 23?m;the cladding layer of the shaped block sample has a strong heat dissipation capability,and the heat dissipation direction has a certain angle with the deposition direction.The growth direction of the columnar crystals is quite different,and the maximum inter-dendritic arm is about 13.70?m..Tensile properties at room temperature were studied,the thin wall and block samples of GH6169 alloy produced by CMT arc additive showed a certain anisotropy.The tensile strength of the formed thin-walled specimen was the largest,774 MPa,and elongation was 27%.The transverse tensile strength of the sample is up to 1099 MPa and the elongation is 18%.The tensile strength of the sedimentary state is mainly affected by the growth direction of the columnar crystal,the Laves phase and the primary dendrite arm spacing.The growth direction of the columnar crystal of the formed thin-walled sample is basically parallel to the deposition direction,and the grain pinning effect of the Laves relative to the deposition direction is more obvious.The growth direction of the columnar crystal of the shaped block sample depends on the heat dissipation condition under the influence of the lap strategy.When the transverse stretch is performed,the pinning of the Laves relative to the grain along the deposition direction makes the material stronger and the shape is worse.The results of heat treatment show that,the higher the solid solution temperature and the longer the time,the more obvious the migration of the columnar grain boundary,and the higher the solubility of the Laves phase.The anisotropy of the bulk sample after heat treatment is lower than the anisotropy of the formed thin wall,and the thin wall is formed.The tensile strength of the specimen in the horizontal direction is up to 1085 MPa,the elongation is about 30%,the tensile strength of the specimen in the deposition height direction is 1222 MPa at maximum,and the elongation is 30%;the resistance of the sample block along the horizontal direction The tensile strength is up to 1367 MPa and the elongation is about 18%.The tensile strength of the sample along the deposition height is 1330 MPa and the elongation is about 17%.