Understanding and Mitigating Hydrogen Embrittlement in High-Strength Carbon Steels for Hydrogen Infrastructure

Hydrogen transport and storage infrastructure needs to urgently evolve. However, hydrogen-induced damage in carbon steels implies a significant risk of failure, with hydrogen embrittlement being a major concern.

Carbon steels are cost-effective and versatile materials that have been used for decades in the gas industry for long-range transport and storage of different gases. Nowadays, they are intended to be used for carrying substantial amounts of hydrogen gas. Identifying the right steels for pipelines and pressure vessels in the upcoming hydrogen economy is a crucial safety measure.

In this project, we aim to analyze various high-strength carbon steels (HSCS) with different microstructures and strengths levels to determine their suitability for service of transport and storage of hydrogen gas. To assess the impact of hydrogen on HSCS, a combination of mechanical testing and microstructural analysis techniques is employed.

“Hydrogen embrittlement is a multidisciplinary field, spanning materials science, fracture mechanics, electrochemistry, and corrosion, among others. To truly understand the problem, one should consider it from all these perspectives”

Eduard Navalles

The metal-hydrogen interaction is being studied by means of solubility, diffusivity and so-called “trapping sites”, preferred locations where hydrogen tends to accumulate. To do so, it is crucial to have a detailed knowledge of the steel’s microstructure, including grain size, its microconstituents, precipitated carbides, processing-induced impurities (inclusions), and interphases.

'Ensuring that the materials used in the hydrogen infrastructure can stand up to real-world conditions is the backbone of a safe energy transition Nuria Fuertes
Mechanical behavior is analyzed using the hollow specimen method (HSM), an in-situ testing technique in which pressurized hydrogen gas is introduced in a hollow specimen. Specimens are tested under slow strain rate testing (SSRT) and low cycle fatigue (LCF) conditions, providing insights into how the different HSCSs behave in a hydrogen gas environment. Fracture mechanics tests, including fatigue crack growth (FCG) and fracture toughness, complement the results.

”Hydrogen gas might be solution to fossil free society, but this dream can make through only by the truly understanding of engineers and materials scientists and solving the challenges with hydrogen embrittlement of metallic materials”

Birhan Sefer

Fractography and hydrogen analysis posterior to mechanical testing provides a better understanding of the failure mechanisms. Scanning electron microscopy (SEM) and light optical microscopy (LOM) are used to assess the degree of embrittlement. Electron backscatter diffraction (EBSD) helps trace the crack propagation path. Additionally, thermal desorption mass spectrometry (TDMS) measures the hydrogen content within the steel, allowing estimation of the critical hydrogen concentration that leads to embrittlement.

By integrating advanced mechanical testing, microstructural characterization, and hydrogen quantification methods, this project seeks to identify HSCS that can withstand hydrogen-rich environments, ultimately contributing to the development of safer and more reliable hydrogen infrastructure for the future.