Preparation Of 316L Stainless Steel Microsphere Powders And Research On Its SLM Forming Test

As a typical manufacturing technology,Selevtive Laser Melting(SLM)can form complex parts.At present,the research on SLM forming technology at home and abroad mainly focuses on the process aspects.However,the research on metal powders for SLM forming is less.The atomization technology has the advantages of high production efficiency,low oxygen content of powders and high sphericity of powders.It is widely used in the preparation of powders making.In this paper,the influence of atomizing nozzle structure on the yield of fine powders was studied.And the effects of different atomization pressure on the size,shape,morphology and microstructure of 316 L stainless steel powders were studied.The effects of SLM forming process parameters and the placement angle on the density,surface roughness and mechanical properties of the samples were investigated to provide technical basis for the application of SLM forming of domestic 316 L stainless steel at low cost.The main conclusions are listed as follows:The 316 L stainless steel powders prepared by the hole seam groove combination of nozzle have the highest yield,and the particle size of the powders decreases with increasing atomizing pressure.The values of the average elongation,the average O.Bluntness and the average Outgrowth of the powders prepared by different pressure are below 0.4,0.6 and 0.2,respectively.The fluidity of the powders under lower atomizing pressure is better and the fluidity disappears when the atomizing pressure is high.The flowability is significantly improved after sieving the fine powders below 25?m.The surface and internal microstructure of 316 L stainless steel powders prepared by different processes are mainly cellular crystal and dendrite.The optimum parameters of SLM forming of the samples obtained by orthogonal test analysis are P = 100 W,v = 450mm/s and s = 0.08 mm.The weld joint of the sample formed under the parameters is about 0.5.The lap is close and the surface is smooth.The density can reach 98.3%.The surface roughness is 16.5 ?m.The tensile strength is 662 MPa.The elongation after the tensile is 33.5%.And the hardness is 211.5 HV.The fracture mode of specimen is ductile fracture.The density of the specimens formed by different placement angles decreases and then increases with increasing angle.The density of the sample at the angle of 30° is the minimum value which is 97.5% and the density of the sample at the angle of 90° is the maximum value which is 98.4%.The surface roughness increases at first and then decreases with increasingangle.The maximum value is 17.9 ?m at the angle of 30° and the minimum value is 10.6?m at the angle of 75°.The tensile strength at the angle of 0° is the highest which is 679.1MPa and the tensile strength at the angle of 90° is the lowest which is 601.6MPa.Most of the sample's elongations are relatively high which can reach 53.3%.The fracture mode of most samples is ductile fracture.There is a small part of cleavage fracture in the sample with inclined angle of 15°.The quality and effect of the 316 L stainless steel impeller parts formed on the domestic Dimetal-80 equipment with the optimum parameters are good.