Investigating the influence of strain rate on hydrogen embrittlement in steel sub-size tensile specimens using 3D X-ray tomography
Luciano Meirelles Santana, Victor Okumko, Andrew King, Thilo F. Morgeneyer, Jacques Besson, Yazid Madi
Abstract
This study investigates the effect of strain rate on hydrogen embrittlement in ferritic-pearlitic E355 steel sub-size 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.