Research on Corrosion Behavior of Zr702 Alloy Welded Joints in Boiling Nitric Acid
The stress corrosion,electrochemical corrosion,uniform corrosion behaviors and failure mechanism of Zr702 alloy joints welded using tungsten inert gas(TIG)were investigated in 8 mol/L boiling nitric acid.The results show that the grains in the fusion zone and heat affected zone(HAZ)of Zr702 alloy welded joints undergo coarsening after welding.The residual tensile stress generates in HAZ,which is reaching 179.68 MPa and 134.94 MPa in parallel and perpendicular to the weld seam,correspondingly.The uniform corrosion rate of Zr702 alloy welded joint is 50%higher than the base material,because that the residual stress in HAZ can induce alloy dissolution corrosion.Under the action of tensile stress,the passive film on the surface of Zr702 alloy welded joint cracks along the direction perpendicular to tensile stress,exhibiting obvious cleavage fracture characteristics,resulting in increasing stress corrosion sensitivity of the joints and a risk of stress corrosion cracking.
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