| The liquid lead-bismuth eutectic alloy(LBE)is considered the primary candidate for the spallation target and coolant material of Accelerator Driven Sub-critical Systems(ADS)due to its excellent physical and chemical properties in the future advanced nuclear fission-ADS tamper system.In the process of circulating cooling,the liquid lead-bismuth alloy will corrode the structural material of the reactor,thus reducing the performance and service life of structural materials and increasing the safety risk of nuclear reactors.The cavitation erosion is one of the corrosion failure behaviors of nuclear materials.When the liquid lead-bismuth alloy flows at high speed,fluctuation of the local pressure will cause cavitation phenomenon,the surface of material is destroyed with the collapse of the bubbles,resulting in cavitation erosion.Numerous nuclear reaction structure components are manufactured and assembled by fusion welding,such as pipe joints,main pump impellers and so on.Because the microstructure of the weld joint is the as-cast structure,the factors of coarse grain,uneven organization and welding residual stress make it a weak area of cavitation erosion resistance.At present,there are few studies on the cavitation erosion of weld joint in liquid lead-bismuth alloy,so it is very important to study cavitation erosion behavior and mechanism of material in liquid lead-bismuth alloy.304 austenitic stainless steel and CLAM steel with excellent performance can become the structural materials of Accelerator Driven Sub-critical System(ADS).According to the requirements of cavitation erosion test in liquid lead-bismuth alloy,a set of ultrasonic cavitation test device was designed independently.In this paper,ultrasonic cavitation test equipment,scanning scanning electron microscopy(SEM)and atomic force microscopy(AFM)were used to study the cavitation behavior of 304 austenitic stainless steel and CLAM steel base metal and weld joint in 550 ? liquid lead-bismuth alloy and the effects of solution treatment on the cavitation behavior of 304 austenitic stainless steel weld joint,then the cavitation erosion mechanism was analyzed.Cavitation erosion degree of 304 austenitic stainless steel and CLAM steel base metal andweld joint was increased with the increase of cavitation erosion time in 550? liquid lead-bismuth alloy cavitation tests.The results show that specimen surface of 304 austenitic stainless steel and CLAM steel base metal and weld joint occurred deformation and work hardening under the impact of bubble collapse,and the cavitation damage on the specimen surface of weld joint is obviously serious on the base metal,the ferrite in weld joint preferentially fell off,the cavitation pits gradually respectively extend to the austenite phase and the martensite phase,and the sample surface roughness increased significantly.The cavitation erosion resistance of CLAM steel weld joint is lower than that of 304 austenitic stainless steel weld joint.This is due to the martensite phase belongs to the hard brittle organization,although it can absorb energy of bubble collapse by dislocation movement and Plastic deformation,because the impact of the bubble collapse is very large,martensite is prone to brittle fracture,which further aggravate the cavitation erosion damage of CLAM steel.After the solution treatment,304 austenitic stainless steel weld due to hardness,the resistance of bubble collapse impact increases,thereby reducing the generation of cavitation pits and expansion.On the other hand,the solid solution treatment reduces most of ferrite phases in the weld joint reducing the cavitation erosion source,and further improving the cavitation erosion resistance of the material. |
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