Toughness and hydrogen compatibility of austenitic stainless steel welds at cryogenic temperatures

A wide range of TIG welds of austenitic stainless steels and filler materials were investigated with respect to their microstructure and cryogenic toughness. Depending on the combination of base and filler material the resulting structure of the weld seam can show either long cross-sectional delta-ferrite dendrites, isolated delta-ferrite islands or no delta-ferrite at all (fully austenitic). The delta-ferrite content varied in a range of 0-12%. An overall correlation between the delta-ferrite content and the Charpy V toughness measured at -269 degrees C could not be found. In all cases the toughness values were greater than 40J/cm(2) at -269 degrees C. The presence of delta-ferrite did not lead to the formation of martensite upon cooling. Charpy V testing at -269 degrees C did not show a significant reduction in toughness compared to testing at -196 degrees C. Using Ni-based fillers can lead to localized hydrogen embrittlement. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.