Strong hydrogen trapping by tangled dislocations in cold-drawn pearlitic steels

The presence of diffusible hydrogen atoms can lead to hydrogen embrittlement in steels, compromising their structural integrity. A potential solution is incorporating strong hydrogen traps into the microstructures to immobilize hydrogen solute atoms and prevent their diffusion towards stress-prone areas where embrittlement is most likely to occur. However, creating materials with effective hydrogen traps usually involves adding expensive alloying elements, which increase the production costs, hindering the adoption of this strategy in the steel industry. Here we show that cold drawing of pearlitic steel rods introduces a high-density of dislocations that accumulate and tangle at cementite-ferrite interfaces; this strengthens the steel and make it less susceptible to embrittlement. We use atom probe tomography to confirm that these tangled dislocations firmly trap hydrogen in a steel that displays low embrittlement susceptibility. Our findings suggest a pathway for producing metallic materials that have an excellent combination of high strength and hydrogen embrittlement resistance, underscoring the potential of using structural defects as cost-effective hydrogen traps.