EFFECT OF HYDROGEN CONCENTRATION AND MnS INCLUSIONS ON THE EMBRITTLEMENT OF A HIGH STRENGTH STEEL

Premature failure or degradation of mechanical properties of high strength steels due to the influence of hydrogen (H) causes significant problems in industries. Among many factors, MnS inclusions play an important role during forming of steels in the stage of rolling, whose presence affect mechanical properties of final products. Additionally, they act as active centers in the capture of molecular hydrogen, thus increasing the embrittlement of the steel. The aim of this paper is to contribute to the understanding of inclusions - hydrogen interaction in a high strength steel. Severe hydrogen loading of steel was performed by cathodic electrolytic charging with the addition of poisons that inhibit the recombination reaction of hydrogen and weaken the atomic bonds of the metal. Subsequently fractographic and structural aspects were analyzed using microscopy and energy dispersive spectrometry. The type, morphology and distribution of cracks was related to the amount of hydrogen added. Sulphide inclusions were found to play an important role stimulating the nucleation of cracks.