Microstructure And Mechanical Properties Of IC10/GH3039 Electron Beam Welding Welded Joints

In this paper,the vacuum electron beam welding of GH3039/GH3039,GH3039 /IC10,IC10/IC10 superalloy with plate thickness 2mm is studied.The weldability of superalloy IC10 single crystal superalloy is worse than GH3039,and the same kind of IC10 alloy welding joint is prone to solidification crack.There are few reports on dissimilar welding between superalloy and single crystal superalloy at home and abroad.Therefore,based on the comprehensive analysis of microstructure transformation of welded joints,the mechanical properties of welded joints are combined.A set of IC10/GH3039 vacuum electron beam welding process selection method is put forward.In the end,not only the IC10/GH3039 vacuum electron beam welding crack free joint has been obtained,but also the joint has excellent mechanical properties.Firstly,the effects of different process parameters on the microstructure and mechanical properties of the same GH3039 superalloy welded joints are analyzed.By electron backscattering diffraction(EBSD),it can be concluded that there is no small angle grain boundary(<10°)and the highest grain boundary energy range is 40°-50°in the welded joint of GH3039 alloyed superalloy,in which the large angle grain boundary occupies the dominant position.The same kind of GH3039 welded joint with no defect and the highest tensile strength is obtained by orthogonal test.Secondly,the vacuum electron beam welding of IC10/GH3039 dissimilar superalloy is carried out according to the results of orthogonal test optimization,and the welding speed is changed by changing the determining factor of vacuum electron beam welding.The microstructure and mechanical properties of IC10/GH3039 dissimilar superalloy welded joints were optimized.It was concluded that there were no crack defects in dissimilar superalloys at different welding speeds.The annular morphology of the cross section of dissimilar superalloy weld appears similar to "onion ring".It is considered that because the dissimilar metal melts under the action of high energy beam heat source,convection occurs in the melting pool,and different molten metals are not completely mixed.The back scattering diffraction(EBSD)inverse pole pattern of GH3039 side weld fusion line of welded joint can be obtained,and the orientation of grain [001] becomes weaker in the depth Y0 direction.The most easy growth direction is horizontal X0.From the angle of grain orientation difference,it can be obtained thatthere is no small angle grain boundary(<10°)and the highest grain boundary energy range is 80°-90° in IC10/GH3039 dissimilar superalloy welded joints,in which the large angle grain boundary occupies the dominant position.The microscopic morphology of the transmission electron microscope shows that,a large number of dislocations exist in the grain and between grain boundaries,which indicates that the microstructure deformation ability of the weld is compared.The microstructure of the weld can satisfy the strain needed to release the stress by plastic deformation,so the weld does not crack.The mechanical properties of the welded joints of the dissimilar superalloy are lower than that of the base metal of the IC10 single crystal superalloy.The average tensile strength of the welded joints of dissimilar superalloys can reach 768 MPa,reaching 96.2% of the base metal of IC10 single crystal superalloys,and the highest elongation can reach 81.4% of the base metal of IC10 single crystal superalloys.Finally,the same kind of single crystal superalloy IC10/IC10 sheet welded by vacuum electron beam welding has obvious transverse crack defects,although the transverse crack still appears when the welding speed is increased to 2000mm/min.But the transverse crack is improved.The transverse crack produced by welding is scanned by EBSD.From the EBSD morphology,it can be concluded that the orientation of the grain on both sides of the crack is the same and tends to the direction of [101],that is,the crack lies between the grains with the same orientation.Characteristic of intergranular liquid membrane separation,typical solidification crack.In general,the energy between grain boundaries The higher the grain boundary is,the more unstable the grain boundary is,and the higher the atom mobility is,the higher the grain boundary is,when the small angle grain boundary is dominant in the microstructure,the dislocation is easy to be produced in the grain boundary,which makes the dislocation play a major role in strengthening the grain boundary,and when the dislocation is dominant,the grain boundary is prone to crack.On the contrary,when the large angle grain boundary is dominant,the dislocation is not easy to occur,which hinders the crack formation.From the grain orientation difference angle of the same IC10 welded sheet,the high energy and small angle grain boundary(< 10°)appears in the welded joints of the same type of superalloy IC10,so it is easy to produce cracks.