Investigation of mechanical and microstructural properties in joining dissimilar P355GH and stainless 316L steels by TIG welding process

Abstract

In this study, the joining of high-temperature and pressure-resistant P355GH and austenitic stainless 316L steels by the Tungsten Inert Gas (TIG) welding method was investigated in terms of microstructure, mechanical properties, and weld efficiency. Comprehensive tests were carried out for the weld zone, heat-affected zones (HAZ), and base metals. In metallographic characterization research, optical microscope (OM), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX/EDS), X-ray diffraction (XRD), and EBSD analyses were performed. Average grain size and IPF (Inverse Pole Figure) map were determined from the EBSD analysis of P355GH steel, welded zone, heat-affected zones (HAZ), and 316L steel. Vickers microhardness, bending, Charpy V-Notch impact, and tensile tests were performed to determine the mechanical properties of the welded joint and the base materials. According to the EBSD results, the average grain size of the P355GH base metal was 5.13 ± 1 μm, the average grain size of the 316L base metal was 16.33 ± 5 μm, and the average grain size of the weld center was 10.09 ± 6 μm. As a result of XRD analysis, the delta ferrite phase was determined in the microstructure of the welding region. The highest Vickers microhardness value was determined as 268 ± 15 HV at the weld center. In the tensile test results, the highest tensile strength observed in the transverse weld joint was 593.92 ± 06 MPa and rupture occurred in the 316L region. Bending forces were measured as 34.331 ± 10 kN and 32.966 ± 11 kN for transverse and longitudinal welded samples, respectively. The TIG welding process showed superior properties such as toughness, high plastic deformability, and high weld efficiency of 101.89% in the joining of 316L and P355GH materials.