電子ビーム溶接したNi基超合金／合金鋼異材接合部のミクロ組織と引張強度

抄録

Dissimilar joints between Ni-base superalloy, which is available for turbine impeller for turbocharger, and alloy steel were fabricated by electron beam welding and their microstructure and tensile strength at a room temperature were examined. Macroscopic appearance of the weld part was similar in both joints, however, tensile strength of 247 alloy / SCM435H was smaller than that of 713C alloy / SCM435H joint, and feature of hot-tear fracture was more evident in the fracture surface. SEM-EDX analysis for the weld part found that a 10μm wide solute-segregated region traced the weld interface located in the superalloy side. Small hot-tear cracks were observed only in the segregated region of 247 alloy / SCM435H joint. These hot tear is likely to be distributed over single plane, so have significant effect to joint strength in some case of stress direction.