Effect Of Ion Irradiation On Surface Morphology Of CLAM Steel And Corrosion Resistance Of Liquid Lead-bismuth Eutectic Alloy

Lead-based reactors with lead-bismuth eutectic alloy?LBE?as the preferred coolant are one of the primary candidate reactor types for lead-cooled fast reactors and accelerator-driven subcritical systems.China Low Activation Martensitic steel?CLAM?,as the first generation of reduced activation ferritic/martensitic Steels?RAFMs?independently developed by China,is an important candidate structural material for lead-based reactors.During its service in the reactor,it is subjected to strong neutron flow irradiation and strong liquid LBE corrosion.Combining the radiation damage behavior of CLAM steel in lead-based reactors with the corrosion performance of liquid LBE,the mutual influence mechanism was analyzed to provide technical data and theoretical basis for the future development of lead-based reactors.In this paper,the high energy He⁺ion beam was first used to irradiate the CLAM steel samples,and then the static corrosion test was carried out in the oxygen-saturated liquid LBE at 550?.Various characterization test methods such as scanning electron microscopy?SEM?,x-ray diffraction?XRD?,energy dispersive spectrometer?EDS?and nano-indentation technology are used to characterize the surface morphology,residual stress,the nano hardness and oxide layer structure after corrosion.Mainly including the following aspects of research work:?1?Study the effect mechanism of irradiation doses on the surface morphology and residual stress distribution of CLAM steel samples.High-energy He⁺ion beam irradiation tests were carried out on the surface of CLAM steel samples at room temperature under 4×10¹66 n/cm²,2×10¹77 n/cm²,1×10¹⁸n/cm².The results of the study found that the maximum damage caused by the radiation doses of 4×10¹66 n/cm²,2×10¹77 n/cm² and 1×10¹88 n/cm² were 1.73 dpa,8.67 dpa and43.35 dpa.The irradiation of He⁺ions would cause the diffraction peak of the crystal surface of CLAM steel?110?to shift to a high angle.Angular offset and the increment of surface compressive stress increase with increasing radiation dose.The irradiation of He⁺ions would cause sputtering phenomenon on CLAM steel sample surface.With the increase of the irradiation dose,the degree of surface damage increased,the effect of bombardment sputtering was more obvious,the surface roughness continued to increase,but the growth trend slowed down.?2?Study the effect mechanism of irradiation doses on irradiation hardening.Nanometer indentation hardness tester was used to measure nano hardness on the surface of CLAM steel samples,which irradiated with high energy He⁺ion beam with irradiation doses of 0,4×10¹66 n/cm²,2×10¹77 n/cm² and 1×10¹88 n/cm².The results of the study found that in the process of nano-hardness measurement,there were size effect of back indentation and size effect of indentation.With the increase of He⁺ion irradiation doses,the nano-hardness and Young's modulus of the sample surface both increased.Using the Nix-Gao model to correct the nano-hardness,it was found that the degree of radiation hardening of CLAM steel was not linearly related to the amount of radiation damage,but a fractional power function relationship.?3?Study the effect mechanism of irradiation pretreatment on the corrosion behavior of CLAM steel samples in liquid LBE.CLAM steel samples with He⁺ion irradiation pretreatment doses of 0,4×10¹⁶n/cm²,2×10¹77 n/cm² and 1×10¹88 n/cm² were performed in 550?static liquid LBE for250 h and 500 h corrosion test.After the irradiation pretreatment sample was corroded by liquid LBE,the sample surface oxidized and corroded to form a double-layered oxide layer.The inner oxide layer was?Fe,Cr?₃O₄ layer,and the outer oxide layer was Fe₃O₄ layer.Obviously,in the 250 h corrosion result,it was found that round speckled-like?Fe,Cr?₃O₄ regions appeared in the outer oxide layer.With the increase of irradiation pretreatment doses,the effect of irradiation defects on the oxide layer was obvious,and the growth rate of the inner and outer oxide layers was closely related to the number and types of irradiation defects.As the corrosion time increases,the effect of irradiation pretreatment on the oxide layer weakened and disappeared.