Research On Ion Irradiation Damage On Weld Metal Of 316L Stainless Steel By TIG Welding

Nuclear power as a clean energy has received more and more attention.The key structural parts of nuclear power often need to be welded to assemble.The welded joints of nuclear power structural materials need to be serviced under extreme conditions such as high temperature,strong radiation and strong corrosion.The weld metal is one of the weak areas of the welded joint.In the irradiated environment,the microstructure and properties of the weld metal may change.Studying the irradiation behavior of the weld metal of nuclear power reactor materials is very important to the development of nuclear power.316L austenitic stainless steel was widely used in the field of nuclear power.This article will focus on the mechanism of irradiation damage of 316L stainless steel weld metal.316L stainless steel was welded by TIG welding process in the research.Then the weld metal was irradiated with 70 ke V helium ion and 70 ke V deuterium ion,and the 316L base metal and weld metal were irradiated with 150 ke V helium ion.To study the influence law and influence mechanism of the surface morphology and microhardness of the weld metal caused by different irradiation doses.Moreover,investigate the influence mechanism of helium ion irradiation on the surface morphology,microstructure,tensile mechanical properties,corrosion resistance and intergranular corrosion of 316L steel base metal and weld metal.The research results showed that after the three doses of 5×10¹⁵n/cm²,1×10¹⁶n/cm²and5×10¹⁶n/cm²were irradiated with 70 ke V helium ions and 70 ke V deuterium ions,the weld metal surface morphology produced a large number of small irradiated holes.With the rising irradiation dose,the number of irradiated holes on the weld metal surface increased.Irradiated holes caused the surface roughness of the weld metal to grow,but the increasing trend of the surface roughness of the weld metal gradually slowed down with the increasing irradiation dose.After ion irradiation,the weld metal occurred irradiated hardening.After helium ion irradiation at three doses of 5×10¹⁵n/cm²,1×10¹⁶n/cm²and 5×10¹⁶n/cm²,the microhardness of the weld metal increased respectively:1.58 GPa,1.84 GPa and 2.15 GPa.After deuterium ion irradiation at three doses of 5×10¹⁵n/cm²,1×10¹⁶n/cm²and 5×10¹⁶n/cm²,the microhardness of the weld metal increased respectively:1.02 GPa,1.34 GPa and 1.77 GPa.With the rising irradiation dose,the microhardness of the weld metal increased,but the increase of the microhardness had a non-linear relationship with the increasing of the irradiation dose,it gradually tended to be saturated.Compared with deuterium ion irradiation,helium ion irradiation had a larger hole size,higher hardening rate,and greater irradiation damage.After 2×10¹⁷n/cm²dose of 150 ke V helium ion irradiation,the surface of base metal and weld metal also appeared irradiated holes and irradiated hardening.Helium ion irradiation caused dislocations,dislocation loops and helium bubbles in the base metal and weld metal.The average diameters of dislocation loops produced in the base metal and weld metal were 5.90 nm and 6.12 nm,respectively,and the average diameters of helium bubbles produced in the base metal and weld metal were 0.91 nm and 1.13 nm,respectively.Helium bubbles cause irradiated swelling of the base metal and weld metal.After irradiation,the irradiated swelling rates of the base metal and weld metal were 0.103%and 0.181%,respectively.After 2×10¹⁷n/cm²dose of 150 ke V helium ion irradiation,the irradiation damage caused the deterioration of the tensile mechanical properties of the base metal and the welded joint.The pre-plastic deformation introduced dislocations,which could absorb supersaturated point defects generated by irradiation and improved the resistance of the sample to irradiation.The irradiated holes produced by helium ion irradiation led to the destruction of the dense oxide film on the surface of the base metal and the weld metal,which reduced the corrosion resistance of the sample.The electrochemical corrosion current density of base metal and weld metal increased by5.423×10^-5A·cm^-2and 5.907×10^-5A·cm^-2,respectively.There was no intergranular corrosion in the intergranular corrosion test of the sample after helium ion irradiation,but the irradiated hardening caused a large number of microscopic cracks on the surface.After helium ion irradiation,the microhardness of base metal and weld metal increased respectively:2.33 GPa and2.55 GPa.Compared with the base metal,the coarse grain size and high content of ferrite of the weld metal caused its internal radiation damage after helium ion irradiation more serious.The radiation swelling rate and radiation hardening rate were higher,the corrosion resistance was reduced more,and the radiation resistance was slightly worse.