Microstructure and mechanical response of gas tungsten arc welded joints comprising a UNS N10003 alloy with different heat inputs

UNS N10003 alloys are one of the key structural materials for molten salt reactors. The welds stability of components in the reactors is an important issue because of the requirement for safe nuclear plant operation. In this paper, automatic gas tungsten arc welding was employed to weld a UNS N10003 alloy, the influence of welding heat input on the microstructure, Vickers hardness, tensile properties and impact toughness of the heat affected zone (HAZ) and weld metal in the prepared joints were investigated. Results show an increasing heat input widened the carbides eutectic reaction zone in the HAZ. For all heat inputs, the base metal had the lowest hardness in comparison with the weld metal and HAZ in the joint, while a higher heat input could induce a lower hardness in the weld metal. During tensile tests at 650 °C, the weld joints fractured at the base metal irrespective of heat inputs. Different heat inputs did not show significant influence on the tensile properties and impact toughness. Our work indicates the UNS N10003 alloy has good weldability, and the performance of the welded joint is stable even when using a wide range of heat inputs.