Abstract
Alloy hardened steels offer excellent combination of mechanical properties, hardenability and corrosion resistance. 34CrMo4 is a medium carbon, low alloy steel widely used due to a good combination of high-strength, toughness and wear resistance. However, this steel experiences hydrogen embrittlement (HE), a complex phenomenon depending on the composition and microstructure. This work estimates de loss of the mechanical properties caused by hydrogen in electrochemically H-charged specimens in absence of mechanical stress but also, at low strain rate and constant load. H-charging for 2 and 6 h induce YS losses of about 40% and 71% and UTS losses of 39% and 59%, respectively. The synergistic effect of the stress and the H-charging process leads to a higher loss, 91%, and a faster brittle fracture even though hydrogen content is similar to those firstly H-charged and then tested in air.
Highlights
Global demand for energy will increase in the decades due to a substantial rise of industrial activity and the incorporation of developing and emerging economies to productive resources
Specimens no electrochemically charged have been included for comparison purposes
The average yield strength (YS) and ultimate tensile strength (UTS) values for specimens tested at strain rate (1.6$10Ă6 sĂ1) are about 85 ± 24 MPa and 88 ± 24 MPa, respectively, which corresponds to a decrease of ~91% in tensile strength with respect to H-free 34CrMo4 steel. These results show even greater loss of ductility with respect to the H-charged specimens for 6 h, Fig. 10 (t-test p 1â4 0.015 and p 1â4 0.006 for the comparison with H-charged specimen for 6 h, YS and UTS respectively)
Summary
Global demand for energy will increase in the decades due to a substantial rise of industrial activity and the incorporation of developing and emerging economies to productive resources. The use of fossil fuel energy has led to current situation of CO2 emissions and pollutants responsible for the climate change. In this context, renewable energies appeared as the unique alternative to fight against the global warming. Green hydrogen is one of the most promising options and it is expected their use will drastically increase in the future in order to get the âzero emissions' [2]
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