The effect of electrospark nickel interlayer thickness on the characteristics of Niobium to 410 stainless steel dissimilar laser welding

Dissimilar welding of Niobium to 410 stainless steel has important engineering applications. An interlayer should be used for avoiding or reducing formation of brittle intermetallic phases in weld. In this research the effect of gradual addition of ESD interlayer on the chemical composition, microstructure and mechanical properties of Nb to 410 stainless steel dissimilar laser welding is investigated. The Nb plate with the ESD interlayer thickness equivalent to about 25%, 50%, and 100% of base plate thicknesses on its edge (produced by novel electrospark deposition process) was laser welded to 410 stainless steel by pulsed Nd:YAG laser. The welds were then subjected to metallographic, X-ray diffraction and mechanical tests. Results showed that with an increase in ESD interlayer thickness, the weldability increased due to reduction of brittle μ and ε-Laves intermetallic phases in the fusion zone. Tensile test results of dissimilar Nb to 410 stainless steel weld, showed that the chemical composition of the dissimilar weld zone determines the mechanical strength of the joint. Furthermore, in order to reach high mechanical strengths, contact of the weld pool and its solidification on the Nb also has to be avoided due to formation of brittle ε-Laves phase.