Investigations of Microstructure and Mechanical Properties of 60-mm-Thick Type 316L Stainless Steel Welded Plates by Multipass Tungsten Inert Gas Welding and Electron Beam Welding for Fusion Reactor Applications

Austenitic Type 316L stainless steel plates of very large thicknesses are considered for use in vacuum vessel fabrication in advanced fusion reactors. The possible options for welding of higher-thickness plates are multipass tungsten inert gas (TIG) welding, narrow gap–TIG welding, and electron beam welding (EBW). The manufacture of double-wall vacuum vessel inner components like keys, shells, and ribs are planned to be fabricated using EBW, and some components like field joints are to be fabricated using TIG welding processes. The present paper reports the fabrication of 60-mm-thick Type 316L stainless steel welded samples with multipass TIG welding and EBW processes and sample property characterization studies. The fabricated weld samples have been tested for weld defects with nondestructive tests using X-ray radiography and ultrasonic scan tests. The welded samples have been characterized for mechanical properties such as tensile, bend, Vickers hardness, and Charpy V-notch impact tests. Microstructure analysis has been carried out for both welded samples for the base metal, heat-affected zone, and weld zone. Impact-tested sample fracture analysis has been done by scanning electron microscopy.