Microstructure and Mechanical Properties for the Dissimilar Joining of Inconel 718 Alloy to High-Strength Steel by TIG Welding

The dissimilar lap joint was investigated among Inconel 718 and high-strength steel using tungsten inert gas welding. The weld zone has an austenitic microstructure with the existence of secondary phases. The distribution of secondary phases is observed in the weld zone and the fusion line of the Inconel 718. The elemental mapping from the electron probe microanalyzer has analyzed the development of secondary phases along the grain boundaries and interdendritic regions. The hardness of the weld zone varies due to the presence of secondary phases. The hardness mapping-confirms secondary phases causing the higher hardness in the weld zone. The selected filler metal has good compatibility with the Inconel 718 and the high-strength steel base metal to obtain a high-quality weld. The X-ray diffraction analysis confirms the presence of secondary phases in the weld zone.