Research On Processing Of Nickel-based Parts By Selective Laser Melting

Selective laser melting(SLM)technology is an important development direction of increasing material manufacturing,the technology takes the high energy laser beam as the energy source,and through the two-dimensional selective melting,the accumulated forming three-dimensional entity,compared with the traditional machining,in the processing of complex shape metal parts,forming a complex three-dimensional entity by two-dimensional scanning stratification with “dimensionality reduction”,without processing position limit,forming process simple,wide applicability.Currently,SLM technology has been widely used in aerospace,automotive,medical and other fields,but the study most focused on stainless steel and titanium alloy powder,the less direct forming nickel-based super alloy,the characteristics of melting process,process control and optimization,structure forming need further study.In this paper,the Ni60 powder is used as forming material,and the technology of selective laser melting is studied systematically.Firstly,the temperature field of the forming process is simulated by using the finite element software,and the mapping relationship between the laser energy and the layer of the single layer powder is determined.Secondly,through the experiments on the laser frequency,pulse width,scanning speed and defocusing factors were analyzed by single pass forming,obtained the parameters of the forming process of the size of the weld process;studied the influence law on the forming quality of the track lap and angle rate;determined the relationship between different parameters of energy input line with the powder forming law,and by orthogonal experimental analysis obtained the degree of influence of each parameter on the shape stability;finally,through the optimization of the process parameters,the machining experiments are conducted on typical samples,the forming characteristics of structure with good precision,and the deposition of material hardness,microstructure,density and other indicators were tested and analyzed.The results show that when the overlap rate is 50%,the overlap between adjacent cladding layers closely,forming the best quality;when forming the structure and level of tilt angle greater than 33 degrees,the structure is not easy to tilt forming defects,such as subsidence deformation;The orthogonal analysis shows that the influence order of the forming quality is greater than the pulse width,the pulse width is greater than the laser frequency;the results of hardness test show that forming hardness in two directions is the opposite,parallel section hardness value between 580-620 HV and the parallel section of the hardness value between 610-640 HV,and the interlayer hardness is higher than the inner layer hardness;by selecting appropriate laser processing parameters and scanning path,the compact metal parts were obtained.Due to the thin layer thickness,effectively reduce the defects in the forming process,the microstructure was not obvious,and the density reached 97.49%.