Hydrogen/Radiation Induced Damage And Coupling Effects Study On Selective Laser Melting 316L Stainless Steel

With the development of nuclear industry in our country,higher requirements are placed on the manufacturing efficiency and safety of advanced nuclear materials and equipments.The appearance of selective laser melting(SLM)techniques provides a novel path to design and fabricate the complex equipment used in nuclear reactors Due to the unique processing,the microstructure and performance of SLM alloys will be greatly different from those of materials manufactured by traditional crafts.To ensure the applicability of SLM materials under reactor conditions,it is necessary to conduct research and on hydrogen radiation damage of SLM materials.In this paper,SLM and CR 316L stainless steel(SS)was selected as the research object and a comparative reference to study the effects of hydrogen and radiation damage.The main conclusions are as follows:(1)316L SS was prepared using selective laser melting technology.The microstructure of the material was characterized by multi-scale methods,and the mechanical properties and corrosion resistance of the formed samples were also tested.The results showed that huge amount of cellular subgrain boundaries,amorphous nano-oxide inclusions and high-density dislocation structures are distributed in the forming material.The above structures form a special micro-nano interface structure in SLM 316L SS.Compared with CR 316L SS,SLM 316L SS has excellent strength and corrosion resistance,but its ductility is not as good as the CR one.In addition,SLM 316L SS shows anisotropy in microstructure,mechanics and corrosion resistance.The preferred orientation of the grains on the scanning surface is<101>,and the preferred orientation of the deposition surface is<001>.The scanning side has better mechanical properties and corrosion resistance than the deposition side.(2)For SLM and CR 316L stainless steels,the hydrogen permeability at different temperatures was tested by gas phase hydrogenation and electrochemical hydrogenation.Multiple characterization methods were used to characterize the microstructure and macroscopic changes of the two steels before and after hydrogenation.The result showed that the subgrain boundary can act as a fast diffusion channel for hydrogen diffusion in the material,effectively improving the hydrogen diffusion coefficient of SLM316L SS.Compared with CR 316L SS,SLM 316L SS has a larger volume fraction of hydrogen-induced defects,and its mechanical and corrosion resistance decreases more significantly after hydrogenation.Resistance of SLM 316L SS to hydrogen damage is not as good as CR 316L stainless steel.(3)SLM and CR 316L SS were irradiated by Xe²³⁺at room temperature and 350?,and the microstructure,mechanical properties and corrosion resistance of the materials were investigated through various test methods.Compared with CR 316L SS,SLM 316L SS has more excellent resistance to radiation-induced phase transformation and hardening due to the effect of subgrain boundaries to enhance stack fault energy and refine grains.However,due to the difference in dislocation density,swelling in SLM 316L SS was earlier than that in CR 316L SS at room temperature.The difference in swelling rate between the two steels decreased at 3.7 dpa at 350?,both being 1%.Under the irradiation condition in this paper,the corrosion performance of CR 316L SS decreased,while that of SLM 316L SS deteriorated only under the irradiation at 350?3.7 dpa.(4)Molecular dynamics simulation method is adopted to explore the influence of hydrogen atoms on the formation and evolution of radiation-induced defects.Various experimental methods were used to characterize the microstructure and mechanical properties of two 316L stainless steels under the coupled damage conditions of hydrogen and radiation,so as to verify the SLM stability of 316L stainless steel under the condition of the coupling damage.Molecular dynamics simulation results showed that Hydrogen suppresses annihilation of radiation-induced Frank defect pairs.The experimental results showed that the defect delamination occurred in two 316L SSs under the coupling damage.The number density and size of dislocation loops are larger than that under irradiation alone.Compared with CR316L SS,SLM 316L SS has a more excellent mechanical stability under coupled damage conditions.In this paper,the hydrogen and radiation resistance of SLM 316L SS was studied,and it provides an important experimental reference for the hydrogen and radiation damage mechanism of the nuclear equipment fabricated by AM,which has important significance and value.