Research On The Microstructure Of CLAM Steels TIG Joint And Corrosion Behavior In Static Lead-bismuth Alloy At 550℃

CLAM steel is one of the fusion reactor blanket candidate materials because of it has excellent high temperature mechanical properties and high temperature creep properties. It’s critical to resolve the fusion reactor blanket to put fusion energy in practice. Weld is one of the essential processes in the fusion reactor construction process due to its complexity, so welding of CLAM steel is determined to whether it can be used in fusion reactor. As the candidate materials of first wall of fusion reactor blanket, in the working process, it inevitable to contact with the liquid metal cooling agent. liquid LBE is fusion reactor coolant candidate material, so research on the corrosion behavior of CLAM steel weld joint in liquid LBE also necessary.CLAM steel is welded by welding wire as filler materials,which are prepared in advance with a variety of W content.1.5%, 3%, 4.5%. The amount of WC precipitation increased with the W content increasing in the scale of experimental design. When the addition of W is 3%, the fine lath microstructure appeared in the welding seam, and the welding seam has the maximum tensile strength, in particular, the average tensile strength has reached 671.6Mpa.When the content of W is 4.5%, hardness of the welding seam reached the top. Moreover, M23C6 carbide is observed along the welding seam, while the main element of M represent Cr, Fe, W or Mn. Contrast to the results of those for post-welding heat treatment at 760℃ for 1h, the impact absorbed energy of weld seam without heat treatment is only 10 J, while the opposite is 110 J.Hence,post-welding heat treatment can greatly increase the impact toughness, and improve the impact absorption energy of the welding seam significantly.3mm-thick CLAM steel was also welded with different heat inputs, when welding line input was 1.32KJ/mm,2.31KJ/mm,the delta ferrite content was 1.6%,3.5%,respectively. The delta ferrite content increased with the welding heat input increasing. The results showed the V content has significant effect on the delta ferrite content,and delta ferrite content increased with the increase of V content in the welding line. When the welding heat input is 2.31KJ/mm, the V content in the filling material increased from 0.20% to 0.50%, and the weld ferrite content increased from 3.5% to 5.7%.The delta ferrite mostly distributed in the original austenite grain, thus reducing the impact toughness of weld seam of CLAM steel. In order to control the delta ferrite content efficiently, V content in the filling materials should not be too much, while minimizing welding heat input in the welding process.After the duration of 500 h and 1000 h of CLAM steel welded joints exposed to the LBE at 550℃,the weight loss were 0.532 mg·cm-2,0.7872mg·cm-2,corrosion rates were 1.0638 mg·m-2·h-1,0.7872 mg·m-2·h-1,and average corrosion depth were 0.64μm、1.0067μm, respectively. Corrosion rate of weld line decreased with time increasing. It was observed that double oxide layer has formed on the surface of weld line. The external oxidation layer is Fe3O4, which is loose in texture and with some pores, and the internal oxide layer is FeCr2O4. It’s considered that oxide film is protective on the matrix to some extent, and the internal oxidation layer on the matrix has better protection performance.