Investigating the influence of strain rate on hydrogen embrittlement in steel sub-size tensile specimens using 3D X-ray tomography
Résumé
This study investigates the effect of strain rate on hydrogen embrittlement in ferritic-pearlitic E355 steel subsize tensile specimens. Micrometer-scale damage analysis was performed using 3D X-ray tomography. Tests were conducted using an optical extensometry at varying strain rates in air and a 100 bar gas hydrogen atmosphere, including interrupted tests before rupture to capture damage states. Hydrogen reduces ductility, with losses reaching up to 62.8% at slower strain rates. At moderate strain rate, 5 × 10-4 s-1, surface damage manifests as brittle, flat ellipsoidal cracks perpendicular to the tensile axis, while the bulk retains ductile damage with prolate voids aligned longitudinally. Hydrogen-enhanced internal shearing leads to damage coalescence via slant fracture of the ligament between surface cracks and internal voids. At low strain rates (1 × 10-5 s-1), deeper hydrogen diffusion induces brittle flat ellipsoidal cracks both at the surface and in the bulk.
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