体能量密度对316L不锈钢SLM成形缺陷的影响OA

Regarding the correlation mechanism between process parameters and defect evolution in the selective laser melt-ing(selective laser melting,SLM)forming of 316L stainless steel for nuclear fuel assembly tube seats,this study,through or-thogonal experiments and multi-scale characterization,revealed the regulatory laws of volumetric energy density(Ev)on forming quality and defect behavior.The results indicated that when Ev=102.88 J/mm3(P=250 W,V=0.9 m/s,T=30 μm,H=90 μm,θ=67°),the formed components had the best comprehensive performance,with a density of 99.78%,a top surface roughness Ra of 7.49 μm,and a porosity of 0.16%,meeting the engineering standard of nuclear component density>99.5%.The defect evolution presented significant interval characteristics:in the low Ev interval(<68.87 J/mm3),the porosity de-creased sharply from 18.2%(Ev=44.92 J/mm3)to 0.54%,mainly attributed to the elimination of incomplete fusion defects;in the high Ev interval(>104.38 J/mm3),the porosity fluctuated between 1.21%and 1.88%,related to the splashing and ag-glomeration of gas pores caused by unstable molten pools.µ-CT analysis showed that the intermediate area of the formed components had fewer pores,while the top and bottom areas had more 5-15 μm spherical pores;in the high Ev(134.20 J/mm3)case,the pore distribution was regular,but local molten pool instability led to gas agglomeration,forming large irregu-lar pores.Furthermore,residual oxygen in the powder and the Si element tend to segregate to form sub-micron-sized oxide inclusions.The study has revealed the regulatory role of Ev in defect types,distribution and formation mechanisms,provid-ing a process optimization strategy and theoretical support for the high-precision and high-reliability SLM manufacturing of key components of nuclear fuel assemblies.