Research On Mechanical Properties Of 316L Stainless Steel By Selective Laser Melting Under Different Forming Strategies

Selective Laser Melting(SLM)is one of the most cutting-edge rapid prototyping technologies,which can fabricate all kinds of complex parts with high density and excellent mechanical properties directly and easily.It has a broad application prospects in the biomedical,aerospace and custom crafts.Among them,316 L stainless steel by SLM forming has a good biocompatibility,as the internationally recognized surgical implant preferred materials,widely used in clinical.In addition,316 L stainless steel is often used as seawater desalination,crude oil processing,nuclear power pines and other device material because of its resistance to corrosion,widely used in industrial applications.In the above application,the mechanical properties of the SLM forming parts are the performance index that the researchers focus on.However,due to the hierarchical manufacturing principle of SLM,there are obvious anisotropy in mechanical properties such as tensile properties and impact properties of SLM forming materials under different forming strategies,which brought difficulties for its practical application.So it is very important to study the mechanical properties of the SLM forming parts under different forming strategies.In this thesis,316 L stainless steel powder was used as the material to study the mechanical properties of SLM forming parts,mainly studied the influence of forming direction and notch production on the impact properties of 316 L stainless steel formed by SLM and the influence of forming direction on the tensile properties and density of 316 L stainless steel formed by SLM.The results showed that: SLM forming direction has a significant effect on density and mechanical properties of samples.Compared to horizontal specimen that vertical to Z-axis,vertical specimen that paralleled to Z-axis has a higher density,significantly lower impact performance,enhanced tensile strength,reduced yield ratio and increased elongation;For the horizontal specimens at different angles from the X axis,the mechanical properties of the specimens at 0 ° and 90 °to the X axis are close,while the mechanical properties of the specimens at 30 ° to the X axis are slightly worse.The processing method of V-shaped impact notch has an effect on the mechanical properties,whether it is impact toughness or the strength and plasticity of the tensile specimen thus processed.Compared with the impact notch of SLM,the impact performance of the sample is improved by about 20% through the follow-up machining.At the same time,the tensile strength of the horizontal tensile specimen is obviously improved and the elastic modulus is greatly improved.The rate is enhanced and the plasticity is better through the follow-up machining.The microstructure of parts formed by SLM show that under the same process parameters,the SLM forming parts are overlapped with the cladding layer,and the defects between the scanning lines are more.The presence of internal defects in the bearing section leads to a decrease in mechanical properties.The fracture of the SLM forming parts is characterized by ductile fracture,and the fracture is composed of round or nearly round oval dimple.All in all,this paper systematically studied the mechanical properties of 316 L stainless steel,providing an effective reference for the safety and reliability of its production.