Abstract
In this study, single-edge notched tensile (SENT) specimens machined from a quenched and tempered CrMoV steel plate were hydrogen pre-charged using two different methods: in a high pressure and high temperature hydrogen reactor (19.5 MPa and 450 °C); and using an electrochemical method (2 M H2SO4 + 0,25 g/l As2O3, under a current density of 2 mA/cm2). The thickness of the specimens was only 1 mm in order to facilitate hydrogen entrance in a short time and the fracture J resistance curves were obtained using digital image correlation (DIC) to measure crack growth. The effect of both hydrogen pre-charged methods on the fracture toughness results was analysed, as was the influence of the applied displacement rate. Embrittlement indexes increase as the displacement rate decreases, with maximum embrittlement indexes of 20% and 84% being respectively measured for gaseous and cathodic pre-charging in tests performed at a displacement rate of 0.01 mm/min. Significant differences in the operative failure micromechanisms in the samples pre-charged via both methods were also detected and hydrogen embrittlement theories (hydrogen-enhanced localized plasticity, HELP, and hydrogen-enhanced decohesion, HEDE) were evaluated by mapping the strain distribution in the crack tip process region by means of DIC.
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