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 δδ-ferrite dendrites, isolated δδ-ferrite islands or no δδ-ferrite at all (fully austenitic). The δδ-ferrite content varied in a range of 0–12%. An overall correlation between the δδ-ferrite content and the Charpy V toughness measured at -269∘C could not be found. In all cases the toughness values were greater than 40J/cm2 at -269∘C. The presence of δδ-ferrite did not lead to the formation of martensite upon cooling. Charpy V testing at -269∘C did not show a significant reduction in toughness compared to testing at -196∘C. Using Ni-based fillers can lead to localized hydrogen embrittlement.