Influence of Thermal Aging on Metallurgical, Mechanical and Corrosion Performance of Electron Beam Welded 18mm Thick AISI 316

摘要

The electron beam welding technique was employed to fabricate 18 mm square butt welds of 316 austenitic stainless steel plates. These welded joints were examined for their metallurgical properties (ferrite content, macrostructure, microstructure and microhardness), mechanical properties (tensile and impact) and corrosion behavior in as-welded state and after thermal aging treatments viz. 750 degrees C/24 hours and 750 degrees C/300 hours. The microstructure of the weld zone was characterized by skeletal, lathy and lacy ferrite in an austenitic matrix. The percentage elongation in as-welded state at the bottom region of the welded joints was 14% higher as compared to the top region. The weld zone had better immunity to intergranular corrosion than the fusion boundary region. Thermal aging treatments enhanced the precipitation of Cr rich carbides, which influenced the mechanical properties and corrosion behavior. The aging treatments reduced the impact toughness, the maximum fall recorded was 63% at the top region of the welded joint after aging at 750 degrees C/300 hours. Further, the Cr rich carbides degraded the intergranular corrosion resistance, the extent of this was more in the fusion boundary region followed by the weld zone and the region adjacent to the fusion boundary.