Study On Microstructure And Properties Of TZM Molybdenum Alloy By Electron Beam Wire Deposition Additive Manufacturing

TZM molybdenum alloy is one of the most widely used high melting point alloys and has a wide range of applications in aerospace,military and nuclear industries.The traditional TZM alloy requires expensive molds in the preparation process,the process is very complicated,the cost is high,and it is difficult to prepare three-dimensional parts with complicated shapes.The electron beam wire deposition?EBWD?process can solve this problem well.It has the advantages of large energy input,high deposition efficiency,good vacuum cleanliness,and direct molding of complex parts.It has unique advantages in direct molding of refractory alloys.In this paper,TZM alloy was prepared by electron beam wire deposition process.The macroscopic morphology,microstructure,mechanical properties and internal defects of the deposition layer under different process parameters?scanning path,beam density,printing speed and wire feeding speed?were studied.Firstly,the effects of process parameters on the macroscopic morphology of the deposition layer were studied.The study found that the deposition layer using the round-trip scanning path has a better macroscopic morphology.As the beam density increases,the width of the deposition layer layer increases,and the height decreases.When the printing speed increases,the width of the deposited layer decreases,and the height remains substantially unchanged.At the same time,when the wire feeding speed increases,the height of the deposited layer increases,and the width is basically constant.The influence of process parameters on the microstructure of the deposition layer was studied.When the beam current density is small,the deposition layer is mainly composed of irregular massive grains,and the distribution is uneven and there is no obvious law.When the beam current increases,the grains tend to grow in columnar crystals.The increase in printing speed is also conducive to the formation of columnar crystals in the deposition layer,which is preferentially grown mainly in the[001]crystal orientation,and the effect of the wire feeding speed is relatively small.There are no obvious dispersion-enhancing particles in the deposition layer under different process parameters.At the same time,the burning loss of Ti is very serious.The Ti added to the wire does not have a good strengthening effect.The mechanical properties of the deposition layers under different process parameters were studied.There is no significant change in the hardness of the deposited layer,which is basically between 150 HV and 170 HV.There is a certain anisotropy in the compressive properties of the deposited layer.The compressive yield strength in the Z direction is higher than the compressive yield strength in the X direction.The highest compression yield strength is around 340MPa.The compressive yield strength of the deposited layer is significantly reduced after the remelting process.The formation mechanism of the internal pores defects in the deposition layer and the influence of different process parameters on the distribution and quantity of the pores were studied.The formation of pore is mainly caused by the volatilization of trace impurity elements,alloy element Ti and MoO₃ formed by processing.Increasing the beam density and printing speed will effectively reduce the pores inside the deposition layer.The proper increase of the wire feeding speed is beneficial to the reduction of the pores.However,when the wire feeding speed continues to increase,the pores inside the deposition layer will increase significantly,and there is a critical value.The remelting process can effectively reduce the porosity defects inside the deposition layer.