Study On Electrochemical And Tribological Properties Of Three Nuclear Power Structural Materials

During the operation of the reactor,the structural components in the reactor have been in the water environment with high temperature,high pressure and high radiation for a long time,and there are failure problems such as corrosion and wear,such as fretting wear of fuel rod cladding tube and heat transfer tube caused by flow induced vibration,and stress corrosion cracking of control rod drive mechanism components affected by coolant chemistry and irradiation effect.This paper mainly carries out relevant experiments on the service performance of three typical nuclear power materials,and studies the corrosion resistance of Stellite6 alloy（oxyacetylene welding,electron beam welding,casting and forging）with four different preparation processes in simulated primary water medium;The effects of two welding processes（oxyacetylene welding and electron beam welding）on the corrosion resistance of 304ln stainless steel were studied;The fretting corrosion behavior of FeCrAl alloy in simulated primary water environment was studied.The main conclusions are as follows:（1）The corrosion resistance of Stellite6 alloy prepared by four different processes was studied.The microstructure is mainly composed of Co rich matrix phase,intergranular CR rich carbide precipitation phase and a small amount of w-rich carbide,and the size and distribution of carbide affect its hardness.The change of p H value of1200 mg/L H₃BO₃+2.2 mg/L Li OH aqueous solution significantly affects the corrosion resistance of Stellite6 cobalt-based alloy.This is due to the differences in the dissolution rate of metal elements and the stability of passive films in cobalt-based alloys under different p H environments.（2）The corrosion resistance of 304ln stainless steel with two welding processes was studied.The weld area has good compatibility,and element diffusion occurs in the area near the fusion line.Electron beam welding samples have good intergranular corrosion resistance,while oxyacetylene welding samples have more serious corrosion and obvious grain shedding with the increase of immersion time.The polarization curve test shows that the electrochemical corrosion performance of the heat-affected zone of304LN stainless steel under the two welding methods is significantly lower than that of the substrate.（3）The fretting corrosion behavior of FeCrAl alloy was studied.In the process of fretting corrosion,with the increase of displacement amplitude and normal load,the smaller the open circuit potential of FeCrAl alloy,the greater the corrosion tendency;in the process of fretting operation,the open circuit potential first decreased and then gradually became stable.As the displacement amplitude decreases or the normal load increases,the fretting operating condition changes from a complete slip region to a partial slip region.During the fretting corrosion process,the wear mechanism of FeCrAl alloy is oxidation wear,abrasive wear and a small amount of peeling off.