Laser welding of niobium to 410 steel with a nickel interlayer produced by electro spark deposition

Abstract

Some combination of metals such as niobium to stainless steel cannot be joined directly by laser welding due to formation of deleterious phases. On the other hand placement of a narrow strip of a third alloy between the two metals can introduce many technical and availability limitations. In this work, a more versatile method is developed using electrospark deposition (ESD) for facilitation of subsequent Nb to 410 stainless steel dissimilar laser with minimum heat input successfully. The 1mm Nb plate edge was clad by Alloy 82 using a 4mm round electrode by ESD process. The layer has minimum dilution with Nb while having a metallurgical bond. It exhibited a fine cellular structure with Laves phase particles with 30–50nm in diameter. The Nb plate with edge built up was then laser welded to 410 stainless steel using a 1KW fiber laser machine. The presence of the interlayer material suppressed the formation of NbFe intermetallic in the laser fusion zone and increases weldability. Tensile test of dissimilar laser weld with the nickel base ESD interlayer exhibited an ultimate strength of 285MPa with the failure located at the Nb side and not in laser weld metal or at the ESD interface.