Study On Thermal Aging And Corrosion Resistance Of New Austenitic Stainless Steel

After decades of development of nuclear power main pipeline,the main pipeline materials are updated with the vigorous development of nuclear power industry.From the initial cast steel,duplex stainless steel to the overall forged 316 LN,the development of each generation of nuclear power technology puts forward stronger requirements for the material properties of the main pipeline.The main pipeline materials work under high temperature,high pressure and high temperature for a long time and face thermal aging And stress corrosion.Therefore,the material of Nuclear Piping requires that it has strong resistance to stress corrosion and anti-aging.It also requires a certain degree of strength and toughness to meet the requirements of nuclear power daily work and ensure the safe operation of nuclear power.In this paper,a new austenitic stainless steel main pipe material is designed.By adding nitrogen,the microstructure of the new austenitic stainless steel before and after thermal aging is studied,and the ability of aging and stress corrosion resistance of the new austenitic stainless steel is evaluated.The influence of nitrogen on the mechanical and corrosion properties of stainless steel is compared.After the new austenitic stainless steel was aged at 350 ℃,no obvious aging phenomenon was found within 3,000 h.There is no precipitate,and the microstructure changes little before and after thermal aging.Because of the solid solution strengthening effect of nitrogen element,the strength of stainless steel is improved.The new composition austenitic stainless steel has good toughness,and there is no decrease of toughness within 3,000 h of thermal aging.The potentiodynamic polarization curve and electrochemical impedance spectrum of the new composition stainless steel were measured by RST5200 F electrochemical workstation.The results show that the pitting corrosion resistance of the material is improved with the increase of nitrogen,and the corrosion resistance of the material decreases after thermal aging.U-ring test and slow strain rate tensile test show that the stress corrosion sensitivity of austenitic stainless steel with new composition is low,and grain refinement can reduce the stress corrosion sensitivity.