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New Study Sheds Light on Hydrogen Embrittlement in Metals

When selecting materials for infrastructure projects, metals are typically chosen for their durability. However, in hydrogen-rich environments, like water, metals can become brittle and fail. This phenomenon, known as hydrogen embrittlement, has perplexed researchers since the mid-19th century due to its unpredictable nature. A recent study published in Science Advances brings us closer to predicting this phenomenon with greater accuracy.

The research, led by Dr. Mengying Liu from Washington and Lee University in collaboration with Texas A&M University researchers, focused on the formation of cracks in initially flawless nickel-base alloy samples (Inconel 725), renowned for its strength and corrosion resistance. The study critically examined several hypotheses explaining hydrogen embrittlement, particularly the hydrogen-enhanced localized plasticity (HELP) hypothesis. It concluded that HELP is not applicable to this nickel-based alloy.

Plasticity involves irreversible deformation localized to certain points within a material. HELP suggests cracks initiate at these high plasticity points. “Our study is unique in observing real-time crack initiation, and it doesn’t occur at locations of highest localized plasticity,” explained co-author Dr. Michael J. Demkowicz, a professor at Texas A&M and Liu’s Ph.D. advisor.

Real-time tracking of crack formation is essential. Post-crack examinations fail to capture hydrogen’s role, as hydrogen escapes the material. “Hydrogen easily escapes from metals, so you can’t figure out what it does to embrittle a metal by examining specimens after they’ve been tested. You have to look while you’re testing,” Demkowicz noted.

This study is pivotal for better predicting hydrogen embrittlement. As we move towards a hydrogen-based clean energy future, current fossil fuel infrastructure could become vulnerable to hydrogen embrittlement. Accurate predictions are crucial to prevent unexpected failures and make a hydrogen economy viable.

Experiments and preliminary analyses for this study were conducted at Texas A&M, with Liu conducting further data analysis and manuscript preparation at Washington and Lee. The paper is co-authored by Liu, Demkowicz, and Texas A&M doctoral student Lai Jiang.

More information:
Mengying Liu et al, “Role of slip in hydrogen-assisted crack initiation in Ni-based alloy 725,” Science Advances (2024). DOI: 10.1126/sciadv.ado2118

Source
phys.org