Simulation On Stress And Deformation Of GH4169 Powder SLM Forming Based On Simufact

The SLM process has the advantages of small heat affected area,flexible process,smooth part-forming surface and complex forming structure,and has been applied more and more widely.As a kind of Ni-based high temperature alloy,GH4169 has been studied more and more in SLM forming parts in recent years,and studies have shown that the properties of SLM forming GH4169 alloy parts is close to those of forgings.At present,great progress has been made in studying the effects of different process parameters on the mechanical properties,microstructures and porosity of the parts by experimental methods.However,few studies have been carried out in this field by numerical simulation.Moreover,the SLM forming parts for simulation are smaller in size,and the most simulation sizes are in the range of several millimeters.In this paper,the inherent strain theory was used to simulate and analyze the stress field of 100 mm × 2mm × 100 mm and 100 mm × 2mm × 300 mm forming parts by using Simufact Additive software specially developed for SLM processing.Orthogonal method is used to design the different process parameters combination scheme,according to the characteristics of molten pool in SLM forming process,Gauss surface heat source model was selected to simulate the size of 10mm×10mm×5mm forming parts.The effects of four processing parameters,laser power,scanning speed,scanning interval and heat treatment keeping time,on the stress field and deformation of forming parts were compared and analyzed.The results show that the order of influence from strength to weakness is laser power,scanning speed,heat treatment keeping time and scanning interval.The larger the laser power and the smaller the scanning speed,the larger the deformation of the forming parts;the larger the scanning interval and the longer the heat treatment holding time,the smaller the deformation of the forming parts.Thus,the optimum process combination scheme for obtaining the minimum deformation and the minimum stress peak value is determined.The optimum process combination scheme is used to further simulate the forming parts of 100mm×2mm×100mm and 100mm×2mm×300mm,and analyze the deformation and stress field distribution law after increasing the forming size.The influence of different support height on the deformation and stress field of the forming part is summarized.The simulation results show that the stress concentration is distributed in the support,and the stress peak rises with the increasing of the printing height,but the distribution of the stress field does not change obviously.When the printing height reaches 30 mm,the stress peak value is 1060 MPa.The stress peak value remains unchanged until the printing height reaches 120 mm.When the printing height exceeds 120 mm but is less than 200 mm,the stress peak value decreases with the printing height.When the printing height exceeds 200 mm,the stress peak value remains unchanged at about 1040 MPa.Therefore,in order to make the stress field in the forming parts evenly distributed and reduce the production cost,the supporting height can be taken as 30 mm.The heat treatment process should be carried out after the printing to reduce the stress inside the structure and prevent the serious residual deformation with the release of the stress after the forming.It also can simulate and optimize the heat treatment process by Simufact Additive software.In this paper,three processing schemes,heat treatment without heat treatment,heat treatment after support-cutting and heat treatment before support-cutting are designed,and the deformation and stress field variation of thin wall structure are studied.The results show that the stress level is higher and the deformation is larger than that at the end of printing.The stress level of the heat treatment scheme after removal is lower,but the deformation is larger.After heat treatment,the deformation of with-heat treatment process is smaller than that of the without-heat treatment plan,and the stress level is the same as that of the heat treatment plan after heat treatment.Therefore,to obtain SLM workpieces with small stress and deformation,the heat treatment process should be carried out after the printing,and then the substrate and support should be removed to obtain the finished parts.