Hydrogen embrittlement of TRIP steel after previous deformation

The aim of the work was to obtain information about the effect of hydrogen in pre-deformed samples made of TRIP 780 steel and during deformation, when retained austenite transforms into martensite. Electrolytic hydrogenation took place both under the simultaneous action of deformation and before the tensile test itself. After hydrogenation, TRIP steel showed an increase in the yield strength and a decrease in the tensile strength. Elongation at fracture also decreased significantly by more than 20 % compared to samples that were only pre-deformed. The occurrence of deformation-induced martensite in the microstructure of TRIP steels significantly contribute to the susceptibility of these steels to hydrogen embrittlement. For samples with 5% predeformation, the value of the hydrogen embrittlement index was found to be 78.1 %, for samples with 10% predeformation it further increased to 86.2 %. From these results, hydrogen led to a degradation of mechanical properties with increasing percentage of deformation and at the same time the obtained results demonstrate a significant susceptibility of TRIP steels to hydrogen embrittlement. The article also contains results of a fractographic analysis, which also showed the occurrence of typical signs of hydrogen embrittlement, which are a quasi-cleavage fracture and fisheyes.