Hydrogen absorption of different welded duplex steels

In this study, hydrogen absorption and storage was investigated for various high-alloyed ferritic–austenitic duplex stainless steels. On account of the specific transformation and solidification behaviour, respectively, of duplex stainless steels as compared to single-phase ferritic and austenitic steels, special conditions have to be considered concerning hydrogen absorption which may ultimately lead to microstructure-dependent hydrogen-assisted weld metal cracking. Hydrogen absorption during welding may occur via the shielding gas, moisture from the surroundings or via the welding filler material. As a contribution to the interpretation and prediction of hydrogen-induced cracking in welded duplex stainless steels, the actual hydrogen absorption via the arc as well as the weld metal hydrogen diffusion was investigated in a duplex stainless steel DSS (1.4462) and in a lean-duplex stainless steel LDS (1.4162). Isothermal heat treatment using carrier gas hot extraction enabled quantification of the amounts of hydrogen trapped in the respective microstructures. The total hydrogen concentrations were found to be nearly identical. Trapped hydrogen was however observed to be dependent on the material and on the microstructure condition. The influence of hydrogen on the mechanical properties of the weld metal was characterized with the help of tensile tests. In addition, hydrogen embrittlement was detected in scanning electron microscopic analyses.