Electron beam and Nd-YAG laser welding of niobium-1% zirconium and molybdenum-44.5% rhenium thin select material

A development study has been completed on autogenous electron beam and Nd-YAG laser welding of niobium-1% zirconium (Nb-1% Zr) and molybdenum-44.5% rhenium (Mo-44.5% Re) thin sheet material. Specimens 0.5 mm thick were welded using both processes in a butt joint configuration. Mechanical tests were performed on welded specimens and their ultimate tensile strengths and percent elongation were determined. Metallographic cross-sections of sample welds showed that electron beam welding resulted in larger grains and an increased heat affected zone compared to laser welded samples. The Nd-YAG laser process yielded a more refined grain structure in the weld compared to the electron beam process due most likely to solidification mode and weld heat input differences. These preliminary studies show that the Nb-1% Zr material can be successfully welded using either welding process. The Mo-44.5% Re material was only successfully welded using the electron beam process. The Nd-YAG laser welded Mo-44.5% Re samples yielded some surface and sub-surface cracks and displayed brittle behavior during mechanical testing of the welds. Additional work will be required to determine the feasibility of obtaining optimum laser welds on the Mo-44.5% Re material.