Microstructural characterization and mechanical performance along the thickness of electron beam welded stabilized AISI 321 stainless steel

Abstract

The Electron Beam welding (EBW) process was employed to fabricate 18 mm thick fully penetrated butt welds of AISI 321 stainless steel. Nail-shaped weld wide at the top and narrow at the bottom was obtained. Characterization of the weld joint was carried out using optical microscopy, scan electron microscopy, X-ray diffraction, microhardness, impact toughness test, and tensile strength test. The microstructure of the weld metal was found to be free from defects like cracks, porosity, etc. The weld metal consisted of the primarily austenitic matrix with skeletal and vermicular morphology of δ-ferrite by the side of the grain boundaries. Carbides of Cr and Ti were found in the weld metal after the thermal aging treatment of 750 °C for 24 hours, as revealed by the XRD analysis. The tensile strength study revealed a maximum strength of 575 MPa at the root of the weld joint in the as-welded state. The maximum impact toughness of 129.3 J was obtained in the top section of the weld in the as-welded condition. The results in terms of structure-property correlate relationship. This study recommends the effectiveness of EBW for joining 18 mm thick AISI 321.