Modeling and experimental comparison of residual stresses and microstructure in UNS S32507 welds using Gas Tungsten Arc and Laser Beam Welding processes

This study presents a comparative analysis of Gas Tungsten Arc Welding (GTAW) and Laser Beam Welding (LBW) on UNS S32507 duplex stainless steel, emphasizing thermal behavior, microstructure, residual stresses, and mechanical performance. A finite element thermal analysis using a Gaussian heat source model was performed to predict heat distribution and cooling rates, which were experimentally validated through X-ray diffraction, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). GTAW produced a broader heat-affected zone (HAZ) with peak temperatures around 1968 °C, slower cooling rates, and tensile residual stresses up to 253 MPa. In contrast, LBW exhibited highly localized heating with fusion zone temperatures peaking at 2436 °C, faster cooling rates (>10 3 K/s), and lower residual stresses of 168 MPa. SEM/EDX revealed coarser dendritic grains in GTAW and refined columnar structures in LBW. Both methods maintained residual stresses within the yield strength limit (550 MPa), ensuring a safety factor of 2.0. Tensile tests revealed ultimate tensile strengths of 795 MPa for GTAW and 855 MPa for LBW joints, indicating superior mechanical properties and refined microstructure in LBW weldments. The refined microstructure and reduced residual stress in LBW underline its superior weld integrity.