Comparison of Low Cryogenic Impact Toughness and Microstructure of GMAW (Gas Metal Arc Welding) and GTAW (Gas Tungsten Arc Welding) Weld Zone in 304L Stainless Steel for Liquid Hydrogen Tank

To combat global climate change caused by CO2 emissions, achieving net-zero emissions through sustainable energy solutions is a global priority. Among alternative energy carriers, hydrogen is a promising renewable energy source due to its efficiency in production, transportation, and storage. Liquefied hydrogen (LH2) transportation is gaining attention as it significantly reduces volume and enhances efficiency. However, LH2 storage containers require specialized materials with excellent cryogenic mechanical properties and hydrogen embrittlement resistance. Austenitic stainless steel (ASS), specifically 304L, is a strong candidate due to its superior mechanical properties at cryogenic temperatures and resistance to hydrogen embrittlement. In fabrication of ASS, Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW) are commonly used. This study investigates the micro structural and mechanical properties in ASS 304L welds using 308L filler metal under these welding processes. Weld bead morphology, microstructural characteristics, and cryogenic mechanical properties were analyzed using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Electron Probe Micro Analysis (EPMA). Additionally, tensile, hardness, and Charpy impact tests at room and cryogenic temperatures were conducted. The results provide insights into the impact of heat input on δ-ferrite distribution, grain structure, and mechanical properties, contributing to the optimization of welding processes for LH2 storage applications.