Numerical and experimental investigation of autogenous GTAW weld between IN 718/ASS 304L

The utilization of Inconel and austenitic stainless steel is essential in high temperature applications, such as power plant boilers, to enhance the performance of structures operating under elevated temperatures. In this study gas tungsten arc welding (GTAW) has been aimed to autogenous weld Inconel 718 (IN 718) and austenitic stainless steel 304L (ASS 304L) of 5 mm in thickness. Numerical modelling of the autogenous dissimilar demonstrates the distribution of the heat generated along the weld produced using ABAQUS software. Detailed microstructural and mechanical characterization were performed on defect free autogenous dissimilar weld. The microstructural analysis examines the heterogeneity in produced microstructure in the weld zone and near weld interfaces. Field emission scanning electron microscope (FESEM) analysis results illustrate the elemental microsegregation (Cr, Nb, Co, Ni and Fe) from base materials to the weld zone producing secondary phases and laves phases. Nb, Mo rich laves phases and carbides are detected in the weld zones distributed uniformly along the grain boundaries. In order to assess the influence of secondary phases on the weld, a series of mechanical characterization tests were conducted. These tests included tensile testing, impact testing, and Vickers microhardness testing. The fractures of the tensile specimen occur subsequent to the weld, following a significant degree of elongation. The highest tensile strength attained for a dissimilar weld is 584.8 MPa, with a maximum elongation of 32.3%. The microhardness analysis reveals a discernible lack of uniformity in the distribution of hardness values across the weld zone because of the inhomogeneity of the microstructure morphology. The charpy impact toughness result shows an impact value of 26 J for the weld center, indicating the brittle character of weld supported by the existence of secondary precipitate and laves phases. The results of the scanning electron microscopy (SEM) failure analysis of tensile and impact specimens reveal the presence of both ductile and brittle characteristics in the fractured samples.