Microstructure and mechanical properties of rhenium and GH3128 superalloy dissimilar welded joints by electron beam welding

This research aims to study the dissimilar welded joint of rhenium and GH3128 made by electron beam welding. The microstructure, solidification behavior, mechanical properties, and Re distribution behavior of the weld were systematically researched. The results showed that an excellently joint is obtained, and no defects such as cracks and pores were found in the weld. But thermal cracks occur on the Re base material under the influence of heat input. The fusion zone was mainly composed of columnar dendrites, while the plane grains grow near the Re-side fusion line (reaction layer), which was always enriched in the Re element. Re is evenly distributed in the Ni matrix as a solid solution element so that the hardness of the joint is always higher than that of the GH3128 base material. The tensile strength of the joint reached 498 Mpa and the elongation was about 3%. The tensile fracture occurred at the position of the reaction layer. The high hardness and brittleness of the reaction layer are attributed to the high content of Re and a lot of low-angle grain boundaries.