| The excellent properties of copper and copper alloys complement the advantages of steel in many areas.In this paper,CMT welder is used to obtain a stable,shallow penetration layer,and then to add CuA18 components to stainless steel,which is of great significance for enriching the wire arc additive manufacturing technology and exploring the copper alloy cladding and additive manufacturing process.Three CMT modes were used for cladding.The thickness,width,substrate depth,and interface layer thickness of the deposited layer under different modes were studied.It was found that using C1 mode(droplet transition+CMT short-circuit transition)got the shallowest depth of substrate melted and the lowest dilution rate.The shear strength of the deposited layers in the three modes is not very different and increases with the increase of the wire feeding speed.Metallographic analysis shows that when the wire feeding speed is small,The iron-rich phase in the deposited layer shows a needle-like shape and a small ball,and it shows a snowflake shape and a needlepoint shape as the wire feeding speed increases,and then the snowflake shape and the needlepoint shape break,and the iron-rich phase after the fracture continues to grow into Ellipsoidal and dendritic.The influence of the process parameters on the formation of the deposited layer under the C1 mode was studied,and the process zone that can guarantee the good single-pass deposition layer was determined.The composition and phase of the various precipitate phases in the deposited layer were studied by SEM spectroscopy and X-ray diffraction.Needle tip,snowflake,and dendritic,which precipitated in higher,is α-Fe phase,which was content of Fe and was mainly solid solution of a certain amount of Cu and Cr element.When the molar ratio of Fe to Cu is about 4:1,Small spherical iron-rich phase is FeCu4,and the precipitation temperature is lower;After melting,the liquid globules form,but they are not sufficiently miscible with the copper-rich phase.The dissolved Cu element is eliminated during the cooling process to form the ε-Cu phase.The effect of inter-layer temperature on the microstructure and properties of additive manufacturing layers was investigated.When the temperature between the layers is room temperature,the additive manufacturing layer made of layer-by-layer commutation on stainless steel exhibits a laminar structure.Each layer consists of four regions with different shapes:the bottom structure is a thick column perpendicular to the boundary line,small columnar crystals that deviate from the vertical direction,finer columnar crystals that have left and right deviations,and interlaminar top structures are equiaxed crystals and horizontally grown columnar crystals.When the temperature between the layers is 200℃,the structure of the layer is not obvious,and the grain direction is in a "chaotic" state.The hardness distribution of the additive manufacturing layer was investigated.It was found that the hardness of the interlayer temperature at room temperature was mostly above 115 HV0.5,and the hardness at 200℃ was mostly below 115 HV0.5.The tensile strength of the transverse additive manufacturing layer is about 390 MPa at room temperature and the longitudinal direction about 350 MPa,both of which are ductile fractures.The transverse tensile strength at an interlayer temperature of 200℃ is about 350 MPa,which is slightly smaller than the room temperature,butThe extension of both is just the opposite.Additive manufacturing thrust chamber was attempted,and physical objects that were basically consistent with the design model were obtained.However,due to the low precision of the equipment control,the surfaces of the manufactured components were rough. |
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