Influence of Ag transition layer on microstructures and mechanical properties of laser welded 304 SS /Nb joint

The laser weldability of niobium to 304 stainless steel is very poor. The Nb/stainless steel joint using direct laser welding process ruptured immediately after welding. The continuously distributed Fe2Nb was the primary reason that embrittled the joint. The silver was selected as the filler metal to join niobium and stainless steel. The weld appearance is good with Ag layer, there are no defects of appearance such as incomplete penetration, burn-through. The hindering effect of Ag transition layer on the formation of Fe2Nb enhances with the increase of thickness of Ag transition layer. And so the strength of joint increases with the thickness of Ag transition layer. The tensile strength of joint is 198 MPa when the thickness of Ag transition layer is up to 1 mm. The formation of brittle Fe2Nb is the key factor to reduce the strength of joint.