Hydrogen Embrittlement of Type 304L Stainless Steel

The ductility of Type 304L and Type 310 stainless steel as measured by tensile elongation can be reduced substantially when high contents of hydrogen are absorbed. Cathodic charging of thin stainless steel foils severely reduced the foils' ductility and tensile strength. Only a very thin surface layer was damaged by cathodically charged hydrogen because the hydrogen diffused very slowly into the metal. The relative loss of ductility caused by cathodic charging of cold worked material depended on the amount of martensitic phases present. The maximum relative loss of ductility was in material that had been cold strained at -196 C (-320 F) and contained large amounts of the martensitic phases (alpha prime, body-centered cubic and epsilon, hexagonal close-packed). The loss of ductility was related to the width and depth of surface cracks observed in mechanically tested hydrogenated material.