High-resolution transmission electron microscope images at increasing magnification scales showing the structural evolution of ball-milled graphite under hydrogen atmosphere for the hardened steel experiment in a planetary ball mill after 5 h (left panels), 17 h (middle panels) and 48 h (right panels). The ordered graphitic plane evolves rapidly toward a turbostratic structure, and, at high milling times, a fully disordered carbon network with a high curvature. We note the progressive contamination of the hydrogenated carbon structure by iron nanoparticles issued from the shattering of the bowl during the milling process, giving rise to dispersed isolated passivated iron nanoparticles.