Chemical heterogeneity enhances hydrogen resistance in high-strength steels

TL;DR

This study introduces a novel microstructural design in high-strength steels, using chemical heterogeneity to trap hydrogen locally, significantly improving resistance to hydrogen embrittlement without compromising mechanical properties.

Contribution

The paper demonstrates that chemical heterogeneity within steel microstructures can be exploited to enhance hydrogen embrittlement resistance, a counterintuitive approach compared to traditional uniform alloying.

Findings

Hydrogen embrittlement resistance doubled in heterogeneous steels.

Chemical heterogeneity traps hydrogen and arrests microcrack growth.

High strength and ductility maintained despite improved embrittlement resistance.

Abstract

When H, the lightest, smallest and most abundant atom in the universe, makes its way into a high-strength alloy (>650 MPa), the material's load-bearing capacity is abruptly lost. This phenomenon, known as H embrittlement, was responsible for the catastrophic and unpredictable failure of large engineering structures in service. The inherent antagonism between high strength requirements and H embrittlement susceptibility strongly hinders the design of lightweight yet reliable structural components needed for carbon-free hydrogen-propelled industries and reduced-emission transportation solutions. Inexpensive and scalable alloying and microstructural solutions that enable both, an intrinsically high resilience to H and high mechanical performance, must be found. Here we introduce a counterintuitive strategy to exploit typically undesired chemical heterogeneity within the material's microstructure that allows the local enhancement of crack resistance and local H trapping, thereby enhancing the resistance against H embrittlement. We deploy this approach to a lightweight, high-strength steel and produce a high-number density Mn-rich zones dispersed within the microstructure. These solute-rich buffer regions allow for local micro-tuning of the phase stability, arresting H-induced microcracks thus interrupting the H-assisted damage evolution chain, regardless of how and when H is introduced and also regardless of the underlying embrittling mechanisms. A superior H embrittlement resistance, increased by a factor of two compared to a reference material with a homogeneous solute distribution within each microstructure constituent, is achieved at no expense of the material's strength and ductility.