Arc Additive Manufacturing Process And Properties Of Wear-resistant Gradient Material

In order to break through the technical bottleneck in China's high-load thin-wall bearing material,this paper aims at the problem of solid-phase compounding of copper/steel bimetal in China,and the advantages of liquid-phase compounding technology such as casting and rolling process in foreign countries,using arc deposition technology to prepare a multi-layer wear-resistant material of"steel substrate/copper alloy/tin-based alloy".The paper firstly studied the basic process of CMT and short circuiting transfer MIG arc deposition of S215 aluminum bronze,SCu5210 tin bronze and CuSn8Al0.5 tin bronze.After obtaining the basic process of copper alloy arc deposition and the evolution of microstructures of claddings,CMT technology was used to arc-deposit tin bronze on 35 steel sheet to obtain copper/steel bimetallic strip,which solved the problems of dilution ratio and porosity of cladding with large aspect ratio deposit.Finally,a tin-based alloy was arc-deposited on the copper alloy to prepare a multi-layer wear-resistant material of"steel substrat/copper alloy/tin-based alloy".The main findings are as follows:Under the CMT process,the dilution of Fe was not obvious due to the low heat input.However,when deposited by the short circuiting transfer process,the claddings of three copper alloys had obvious Fe element dilution.Since Fe has a low solubility in copper,it precipitates as particles in the cladding.Among the three copper alloys claddings,Fe diffused fastest in CuSn8Al0.5 and formed the most particulate phase.When depositing copper alloy on 45 steel thick plate,S215 aluminum bronze did not produce pores due to good fluidity;when SCu5210 tin bronze was deposited by CMT process,the cooling rate was faster due to the small heat input,and a small amount of pores were formed.Increasing the heat input leads to the formation of a large number of pores,and the addition of a small amount of Al effectively improves the tendency to form pores in the tin bronze.Under normal circumstances,the increase of heat input was beneficial to improve the bonding strength between the bimetal layers,and the bonding strength between the S215 aluminum bronze/45 steel was higher than 400 MPa.Only when there were many pores in the cladding,the bonding strength was low,mainly because the tensile strength of the copper cladding decreased significantly.The preparation of copper/steel bimetallic strips requires a deposit with a large aspect ratio and a flat surface.The forming properties of the CMT process are more advantageous than short circuiting transfer.In addition,the CMT process reduced the heat input,had a good effect on shortening the solidification time of the cladding,suppressing the pores,and reducing the dilution of Fe,and was a preferable scheme for performing copper cladding arc deposition on the steel surface.When the deposition current was low?60-90A?,the?-Cu dendrites were obtained in the SCu5210 and CuSn8Al0.5 cladding,and SCu5210 was the intergranular segregation of??+??+Cu₃P and?+Cu₃P.CuSn8Al0.5 was??+??structure segregated between?dendrites.With the increase of current?100-110A?,the dendritic morphology of SCu5210 and CuSn8Al0.5 gradually disappeared.For the 35 steel sheet,the volume fraction of ferrite near the cladding decreased and that of pearlite increased with the increasing of current.Therefore,as the current increased,the hardness of the steel sheet increased correspondingly,and the tensile strength and yield strength of the steel sheet increased,and the elongation decreased.When the current was too large?110A?,austenite grains were coarsened due to large heat input.The high cooling rate and coarse grains promoted the ferrite to form side slats from the grain boundaries,forming widmanstatten structure.The values of tensile strength,yield strength and elongation drastically decreased and showed significant brittle fracture.For the cladding of Sn90.5Sb9.5,the metallographic structure was single-phase?-Sn grain at low current?50-90A?;with the increase of current?100A?,the metallographic structure was black?-Sn matrix and the acicular Cu₆Sn₅ phase distributed thereon,and the presence of the Cu₆Sn₅ phase enhanced the hardness of the cladding.