Hydrogen Trapping and Embrittlement Behaviours in Steels

Abstract

Hydrogen embrittlement is a major challenge for the durability of structural steels used in the emerging hydrogen economy. This thesis investigates how hydrogen interacts with microstructural defects, how these interactions contribute to embrittlement, and how they can be mitigated through microstructural design, with the aim of establishing microstructure–property relationships in hydrogen-containing environments (Chapters 1 and 2).

Using advanced characterization techniques and principles of metal physics, this work reveals how defects such as dislocations, interfaces, and precipitates act as hydrogen traps and influence embrittlement behavior. The concepts of weak and strong hydrogen traps are explored, and a new experimental strategy is introduced to distinguish their respective roles (Chapters 4–6).

By correlating atom probe tomography, transmission-based microscopy, and local mechanical characterization, hydrogen distributions at specific defects are directly linked to deformation behavior, providing an atomic-scale understanding of hydrogen–defect interactions (Chapter 7). The results further demonstrate that strong hydrogen traps can be intentionally activated through microstructural optimization, improving resistance to embrittlement (Chapter 8).

In addition, this work examines interstitial hydrogen solution behavior in face-centered cubic alloys, with the results showing good agreement with theoretical predictions regarding hydrogen affinity. These findings provide new insights into hydrogen partitioning and alloy design. Finally, future directions are proposed for atomic-scale hydrogen mapping using cryogenic APT and for the development of next-generation hydrogen-resistant alloys for advanced energy applications (Chapters 9 and 10).