First 3D real-time imaging of hydrogen’s effect on steel defects unlocks safer hydrogen economy

University of Oxford reveals hydrogen’s atomic-scale impact on metal integrity, guiding future alloy design for resilience.

From University of Oxford 12/09/25 (first released 09/09/25)

An artistic impression of the experiment: 3D rendering of the micro-scale stainless steel grain investigated in this study showing the evolution of defects inside it with time (early – blue lines, later – red lines). The grain is embedded within a polycrystalline bulk sample, as schematically. By focussing a coherent X-ray beam on this grain, a coherent X-ray diffraction pattern can be measured, from which the shape of the grain and the defects inside it can be reconstructed. By continually monitoring this grain while hydrogen is introduced, researchers studied how hydrogen interacts with defects. Credit: David Yang, Felix Hofmann (bubbles graphic sourced from Free PNG Logos, John D.). Credit: David Yang, Felix Hofmann (bubbles graphic sourced from Free PNG Logos, John D.).

In a world-first experiment, the team used an advanced X-ray imaging technique to track how tiny defects inside stainless steel (called dislocations) respond to hydrogen exposure.

This is crucial to understand how hydrogen can cause metals to weaken or fail, and could guide the design of next-generation alloys for a growing hydrogen economy.

Lead researcher Dr. David Yang (Brookhaven National Laboratory) said: “Hydrogen has great potential as a clean energy carrier, but it’s notorious for making materials it comes in contact with more brittle.

For the first time, we have directly observed how hydrogen changes the way defects in stainless steel behave deep inside the metal, under realistic conditions.

This knowledge is essential for designing alloys that are more resilient in extreme environments, including future hydrogen-powered aircraft and nuclear fusion plants.”

As countries aim to transition to fossil-free energy systems, hydrogen has been touted as the ideal fuel for ‘hard to decarbonise’ sectors, such as shipping, aviation, and heavy freight.

However, hydrogen can cause unexpected cracking in metals (known as hydrogen embrittlement) which threatens the integrity of high-pressure vessels, pipelines, and critical components in energy systems.

While engineers have long known that hydrogen affects metal performance, the precise mechanisms at the atomic scale have remained elusive, as hydrogen is very difficult to detect.

Study principal investigator Prof. Felix Hofmann (Department of Engineering Science, University of Oxford) explained: “Using coherent X-ray diffraction, a non-destructive method, we were able to watch atomic-scale events unfold in real time inside solid metal without cutting open the sample.

It has been tremendously exciting analysing this data and piecing together the parts of this scientific puzzle.

Some of the results really surprised us by showing up behaviour we weren’t expecting.”

To uncover what hydrogen does inside the material, the researchers used an ultra-bright beamline at the Advanced Photon Source in the US to focus X-rays onto a single stainless-steel grain, roughly 700 nanometres in diameter.

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They then applied a technique called Bragg Coherent Diffraction Imaging to measure how the internal structure of this grain changed over time.

In this method, the X-rays are scattered by the crystal lattice, creating a complex interference pattern.

This can be reconstructed to reveal the structure of the grain, the crystal defects within it and how they distort the lattice around them.

By imaging the steel grain over 12 hours, the experiment revealed three key changes once hydrogen was introduced:

These findings help explain why hydrogen can lead to unexpected failure in metals since it allows internal defects to move more easily and in ways that are not normally possible.

According to the researchers, the work directly informs how to model and predict material performance in hydrogen environments, feeding into multi-scale simulation frameworks used by industry.

It also points toward potential strategies for engineering novel alloys that offer greater resistance to hydrogen embrittlement.

Professor Hoffman added: “This research is only possible because of the availability of extremely bright and coherent X-ray beams at international synchrotron sources.

The results are highly complementary to information from electron microscopy and simulations.

We are now planning even more sophisticated experiments to study how hydrogen changes other types of defects.

At the same time, we’re also developing models to help industry design complex hydrogen fuel systems.”

The study also involved researchers from Argonne National Laboratory (United States), and University College London.

Researchers at the 34-ID-C instrument, Advanced Photon Source, USA, during experimental measurements. From left to right: Dr. Kay Song, Prof. Felix Hofmann (front), Dr. Guanze He (back) and Dr. David Yang. Credit: Felix Hofmann and David Yang.

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