| During the reprocessing process of spent fuel,the equipment is exposed to high concentrations of boiling nitric acid containing radioactive ions for a long time,which requires strong corrosion resistance to ensure the safe operation of the reprocessing equipment.The high Ta content Ti-5Ta-1.8Nb titanium alloy developed in India has excellent corrosion resistance,but its high production cost makes it difficult for high Ta content Ti-Ta series titanium alloys to adapt to large-scale applications.The corrosion and high cost of materials for spent fuel reprocessing equipment are bottlenecks that constrain the development of China’s spent fuel reprocessing technology.Developing Ti Ta based titanium alloys with low Ta content and high corrosion resistance is one of the key issues that urgently need to be solved to reduce the production cost of spent fuel reprocessing equipment materials and improve China’s spent fuel reprocessing capacity.This paper aims to develop Ti-3Ta-x Nb titanium alloy with low Ta type and high corrosion resistance.The corrosion morphology and surface passivation film of Ti-3Ta-x Nb(x=0,1,3,5)alloy in nitric acid environment were studied,and the corrosion resistance mechanism of Ti-3Tax Nb in nitric acid environment was explored.The influence of Nb element content on the corrosion resistance and mechanical properties of the alloy was revealed.The main conclusions are as follows:(1)The degree of equiaxation of the alloy structure decreases with the increase of Nb content,and the structure gradually presents a elongated strip like structure,which was not detected by XRD analysis β Phase,TEM characterization of Ti-3Ta-1Nb and Ti-3Ta-5Nb showed that the crystal structures of both alloys were closely packed hexagonal crystals α-Ti.(2)Through room temperature tensile testing,it was found that the strength and hardness of the alloy first increased with the increase of Nb content.When the Nb content increased to 5%,the strength and hardness of the alloy significantly decreased;The trend of elongation decreases with the increase of Nb content;The fracture mode of Ti-3Ta-1Nb and Ti-3Ta-5Nb alloys is ductile brittle mixed fracture,while the fracture mode of Ti-3Ta-3Nb is ductile fracture.(3)The corrosion rate of Ti Ta Nb based alloys decreases with increasing Nb content,with Ti-3Ta-5Nb having the smallest change in corrosion rate.The degree of corrosion on the alloy surface decreases with the increase of Nb content,and the Nb element content on the alloy surface gradually increases,resulting in a uniform distribution of various elements on the alloy surface.(4)The corrosion current density decreases continuously with the increase of Nb content;The corrosion potential continuously shifts positively with the increase of Nb content;Adding a certain amount of Nb element can reduce the corrosion current density of the alloy;The Nb element can increase the radius of the capacitive arc,and the polarization resistance Rp gradually increases with the increase of Nb element content.(5)With the increase of Nb content,the Nb2O5 content in the alloy passivation film continues to increase.The addition of Ta and Nb elements makes the alloy passivation film more uniform and dense,and the corrosion resistance of the alloy gradually increases. |
