Chemical heterogeneity enhances hydrogen resistance in high-strength steels

Binhan Sun,Baptiste Gault,Dierk Raabe,Dirk Ponge,Chun-Hung Wu,Ran Ding,Wenjun Lu,Di Wan,Surendra Kumar Makineni,Hao Chen

doi:10.1038/s41563-021-01050-y

Abstract

The antagonism between strength and resistance to hydrogen embrittlement in metallic materials is an intrinsic obstacle to the design of lightweight yet reliable structural components operated in hydrogen-containing environments. Economical and scalable microstructural solutions to this challenge must be found. Here, we introduce a counterintuitive strategy to exploit the typically undesired chemical heterogeneity within the material’s microstructure that enables local enhancement of crack resistance and local hydrogen trapping. We use this approach in a manganese-containing high-strength steel and produce a high dispersion of manganese-rich zones within the microstructure. These solute-rich buffer regions allow for local micro-tuning of the phase stability, arresting hydrogen-induced microcracks and thus interrupting the percolation of hydrogen-assisted damage. This results in a superior hydrogen embrittlement resistance (better by a factor of two) without sacrificing the material’s strength and ductility. The strategy of exploiting chemical heterogeneities, rather than avoiding them, broadens the horizon for microstructure engineering via advanced thermomechanical processing.

Highlights

When hydrogen (H), the lightest, smallest and most abundant atom in the Universe, makes its way into a high-strength alloy, the material’s load-bearing capacity is abruptly lost[1,2,3]
High-strength steels are prone to H embrittlement, as less than 1 parts per million by weight H is often sufficient to result in a dramatic degradation of their mechanical properties[6,7,8,9]
Assisted by Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD), a well-adjusted design of the Mn heterogeneity inside the austenite phase produces a high number density of microscopically confined Mn-rich buffer regions dispersed throughout the sample

Summary

Introduction

When hydrogen (H), the lightest, smallest and most abundant atom in the Universe, makes its way into a high-strength alloy (strength above ~650 MPa), the material’s load-bearing capacity is abruptly lost[1,2,3]. Taking advantage of the alternately arranged dual-phase microstructure (Fig. 1b,c) and its ultrafine grain size (~0.6 μm), we achieved a high number density of γMn-rich (above ~2 × 1018 m–3) dispersed throughout the material.

Results

Conclusion