Electron beam welding of difficult-to-weld austenitic stainless steel/Nb-based alloy dissimilar joints without interlayer

Dissimilar butt welding of Nb-1Zr to the 321 stainless steel was studied using electron beam welding. The aim of this study was investigation of the offset and microdilution effects on the weldability, microstructure and mechanical properties of this dissimilar joint. The offset of 50-50 and welding parameters of 13 mA and 1343 V showed the best weldability and penetration for the joint. The microdilution of Nb in the weld changes by going far from the base metals. The microdilution of Nb is the minimum at root of the weld (∼0.2) leading to formation of less brittle phases. As a result, no cracks are observed at the root. The microdilution of Nb at the top of weld just near to Nb-based alloy at a 200 μm narrow zone under surface increases (∼0.8) which leads to formation of more brittle phases and subsequent microcracks. Applying 200 μm thickness machining on the surface of weld can give a completely free of crack welds that show strength more than the Nb-alloy base. It is concluded that a sound weld can be achieved by 50-50 offset and Nb microdilution less than 0.6. No interlayer and/or transition piece are required, and appropriate mechanical properties can be obtained.