Cryogenic Pressure Vessel Welds: Comparative Evaluation of Ni‐ and Fe‐Based Filler Metals in Automated Vacuum Arc Welding of Dissimilar A352/A738 Steels

This study compares the performance of ENiCrMo‐4 and E308L wires in automatic vacuum arc welding for joining dissimilar A352 and A738 steels in cryogenic pressure vessels. Microstructural analysis and mechanical tests investigate the properties of the joints and their relationship with cooling rate and welding parameters. Due to the 2 mm thickness difference between A352 and A738, the cooling rate on the A352 side is ≈179% higher than that on the A738 side. This difference in cooling rate affects the diffusion layer width and the weld microstructure. In comparison, the ultimate tensile strength (UTS) and yield strength of the joint with ENiCrMo‐4 wire (S1) are 1.4 and 2.4% higher than the UTS and yield strength of the joint with E308L wire (S2), respectively. In the cryogenic impact test, the impact energy of S1 is 69 and S2 is 61 J, which shows a 13% advantage in impact energy for S1. This advantage is due to the stronger bond between Ni atoms compared to Fe atoms because the ratio for nickel is 9% higher than that of iron. This study shows that ENiCrMo‐4 wire is a more suitable option for welding cryogenic pressure vessels than E308L wire due to a 13% improvement in impact properties.