Nitrogen effect on the precipitation of secondary phases and mechanical property of the GTA welded Inconel 718

In this research paper, principal attention is given to the effect of interstitial nitrogen on the precipitation of secondary phases and tensile strength of gas tungsten arc welded (GTAW) Inconel 718. Welding was performed using Ar+(0-5%)N2 shielding gas mixtures. Secondary phases were characterized by optical microscope, field-emission gun scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). The results revealed that with increment of nitrogen content, the volume fraction of Nb-bearing phases like Laves and carbide increased due to increased microsegregation of Nb in interdenderitic region. Moreover, nitrogen was found to have negative role in the size of gamma double prime particles within γ core. According to the tensile test results, Ar+1%N2 weld samples showed the maximum ultimate tensile strength and yield strength compared to other samples. While more nitrogen leads to reduction of both strengths due to increased Laves phase quantity and decreased size of gamma double prime precipitates.