Ions Radiation Damage Effect Of 316L Stainless Steels Fabricated By Selective Laser Melting

The development of nuclear energy is an important energy strategy for our country,and advanced nuclear materials are the basis for the security progress of nuclear power.The appearance of metal additive manufacturing?AM?techniques provides a novel path to design and fabricate the complex equipment used in nuclear reactors.However,obvious differences existing in the process between AM and traditional methods will surely lead to the change in properties,such as the microstructure,irradiation tolerance and so on.At present,the study on radiation damage of AM nuclear materials has not attracted much attention from research institutes.It is of great significance to explore the radiation damage effect and mechanism of AM fabricated alloys to ensure the stability of these materials under the extreme radiation environment.In this study,we presented the helium?He?ions and Fe ions radiation damage of 316L stainless steels?316L SS?,which were fabricated by selective laser melting?SLM?,and the main conclusions were summarized as follows:?1?The 316L SS specimens were prepared by SLM process.The microstructure,mechanical properties and corrosion resistance were characterized in present study.Results suggest that cellular sub-grains exist with an average size of 380 nm,decorated with high density dislocations.In addition,a large amount of spherical nano-size oxide inclusions were also observed.The average size and number density of inclusions were measured approximately 60 nm and 4.12×10²⁰ m^-3,respectively.And the amount of inclusions obtained is approximately 5 vol%.The celluar sub-grains and nano-inclusions form the special microstructure owing to the SLM process.Nanoindentation tests showed the hardness of specimens is 2.6 GPa,and the corrosion potential and corrosion current density are-0.284 V,0.80?A/cm²,respectively.This result indicates that the SLM 316L SS has a good hardness and corrosion resistance.?2?The SLM 316L SS specimens were irradiated by He ions.The effect of irradiation temperature and concentration on the stability of interfaces,the distribution of He bubbles and the radiation hardening were investigated by multiple methods like TEM and nanoindentation.Results show that the special microstructure containing cellular sub-grains and nano-oxide inclusions still distribute in post-irradiated samples.He bubbles formed in the samples with a size less than 1 nm,which were irradiated at room temperature?RT?with the concentration 6.72%.The average size of He bubbles formed in another post-irradiated samples was 1.4 nm and 3.2 nm,which were irradiated at 450°C with the concentration of 0.8%and 4.8%.The results show that the increase of irradiation temperature and dose promote the nucleation and growth of bubbles.In addition,a decrease in the bubbles density and hardness enhancement was also observed comparing with conventional stainless steels,which was irradiated at 450°C with the concentration of 0.8%.A larger density of bubbles appeared to be in immediate the sub-grain boundaries?SGBs?and some bubbles with a larger size surround the nano-inclusions,indicating that the SGBs and nano-inclusions are preferential trapping sites for He.And this special microstructure increases the volume fraction of interfaces,which serve as effective sinks for He atoms and radiation defects,reducing the density of He bubbles,the swelling rate of material and the enhancement in hardness.?3?The SLM 316L SS specimens were irradiated by Fe ions.The effect of irradiation temperature and dose on the microstructure,mechanical properties and corrosion resistance were investigated via multiple methods.Cellular sub-grains and nano-oxide inclusions were stable after Fe ions irradiation at RT and 450°C with the dose of 1 dpa.The average size of dislocation loops increased and the number density of loops decreased with the irradiation temperature growing.GIXRD patterns confirm that 2?of?111?peak decreased,which was attributed to the lattice distortion caused by ions irradiation.As the irradiation dose increased and the temperature decreased,the enhancement in hardness and degradation of corrosion resistance grew.The change was most obvious under the ions irradiation at RT with the dose of 10 dpa.This phenomenon is related to the discrepancy in the density and size of radiation defects under different irradiation conditions.In this paper,the ions radiation resistance of SLM 316L SS was studied,and it provides an important experimental reference for the radiation damage study of the nuclear equipment fabricated by AM,which has important significance and value.