Improving the hydrogen embrittlement resistance by straining the ferrite / cementite interfaces

To couple strengthening with hydrogen-insensitive design in steels, many research employ nanosized carbides to trap hydrogen atoms from diffusion. Herein, by using the pearlite steel featuring with abundant ferrite and cementite interfaces as a model material, we show that by applying a moderate pre-strain on the ferrite/carbide interfaces, hydrogen trapping ability of these interfaces can be uniformly improved, considerably alleviating the hydrogen embrittlement while improving the tensile strength of the steel. Postmortem characterizations on the strained interfaces suggest that interfacial dislocations, carbon vacancies, and disconnections may be held accountable for restraining hydrogen uniformly on the interfaces; nevertheless, formation of slip bands upon large pre-strain localizes the above hydrogen traps at their intersections with the ferrite/carbide interfaces, deteriorating the hydrogen embrittlement resistance. The finding demonstrates a feasible method to tackle the trade-off between strength and hydrogen embrittlement resistance in steels.