Fracture process of C–Mn steel embrittled by hydrogen

Fracture morphologies of tested specimens, by means of the slow strain rate tensile testing, were examined to study fracture modes by using scanning electron microscopy.This study has led to the determination of three categories of specimens: unembrittled specimens, slightly embrittled specimens and severely embrittled specimens. The first category of unembrittled specimens includes specimens tested in air, at potentials of −0.80 and −0.85 V (SCE) with embrittlement ratio (ER) ⩾ 0.97. In the category of specimens slightly embrittled, only the specimen tested at −0.9 V with an embrittlement ratio (ER) of 0.69 is included. The last category of severely embrittled specimens includes the specimens with embrittlement ratio (ER) < 0.69.The fractographic studies are consistent with the embrittlement of steel being due to hydrogen embrittlement. The intergranular and transgranular quasicleavage fracture surface morphologies observed with embrittled specimens are typical and characteristic of hydrogen embrittlement.