Numerical Simulation And Experimental Study Of Selective Laser Melting 316L Stainless Steel Powder

Selective Laser Melting(SLM)is developed by selective laser sintering.It has the advantages of the selective laser sintering,such as,wide range of materials,high utilization rate,complicated molding,simple processing,etc.Because it directly melts metal powder to build parts by laser,and the build parts are superior to selective laser sintered parts.SLM technology is widely used in medical,manufacturing molds,aerospace,etc.The way for building parts has gradually become a research hotspot at home and abroad.At present,there are few studies on the analysis of the surface roughness and density of the formed parts by numerical simulation and experimental methods at home and abroad.Therefore,the basic process parameters range is obtained by three-dimensional finite element numerical simulation of the temperature field of laser melting metal forming process in view of the above.Then,using experiment research the influence of process parameters on surface roughness and density to get great processing parameters,and analyze the effect of SLM processing technology on mechanical property.The research contents are as follows:Firstly,316L stainless steel powder material was selected,and a laser heat source with approximate Gaussian distribution was designed.The parametric design language was used to control the movement of the laser heat source.The numerical simulation of the temperature field of laser selective melting of the powdered material was carried out,and the influence of different laser process parameters(laser power,scanning speed,scanning space,layer thickness)on the temperature of SLM forming was analyzed.It is found that as the laser power increases,the temperature of the node acting on the powder layer increases.As the scanning speed,scanning space and layer thickness are increased,the temperature acting on the nodes of the powder layer decreases.In order to ensure that the stainless steel powder can be formed in the experiment,the laser power,scanning speed,scanning pitch,and thickness of the SLM can be controlled to be in the range of 100~200 W,500~1500 mm/s,0.04~0.12 mm,and 0.03~0.06 mm.Secondly,the SLM150 model equipment was used to test the 316L stainless steel powder to study the factors that can affect the surface quality of the formed part.The single factor control scheme was designed to study the effects of different process parameters on the surface roughness and density of the formed parts,and the various process parameters were integrated to extract the influence of laser energy density on the surface quality of the formed parts.According to the laser energy density,the surface quality of the formed part is divided into three regions.Laser energy density 37.88 J/mm~3~75.76 J/mm~3 is a partially melted unstable region.The laser energy density is 75.76 J/mm~3~151.52 J/mm~3 is the fully melted stable zone,and the laser energy density region is the best.The laser energy density is greater than 151.52 J/mm~3,which is a super-melting zone.The laser energy density is high in this area,the metal powder forming process is severely splashed,and the surface of the formed metal has been burnt.Finally,the relationship between laser energy density,microstructure and mechanical properties in SLM forming is analyzed.The main elements of the formed part are the same as those of the original powder,and the?ferrite in the SLM formed part completely disappears,and only?austenite exists.The microstructure of the formed part is austenite,which becomes larger as the laser energy density becomes larger.When the laser energy density is 119.05 J/mm~3,the internal shape of the formed part is dense,the grain boundary of the structure is not obvious,and the basic non-porous contains the typical cellular structure characteristics of the molten pool.The fractured dimple is more obvious,which is ductile fracture,and its hardness and tensile performance are the best.And the surface line roughness Ra is at least 5.4?m,surface roughness Sa is at least 8.94?m,the density is also 99.66%,the hardness is 330.05 HV,the tensile strength is 693.13 MPa,the yield strength 616.24 MPa and the elongation is 34.60%.