By Muhammad OsamaReviewed by Frances BriggsOct 14 2025New research reveals that while 3D-printed stainless steel performs better mechanically, it becomes more prone to hydrogen damage, raising critical questions about hydrogen-ready infrastructure.
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A recent study in the journal Metals comprehensively investigated the effects of hydrogen and hydrogen-blended natural gas on additively manufactured (AM) 316L stainless steel in oil and gas applications.
As hydrogen is increasingly integrated into energy systems, understanding hydrogen embrittlement becomes crucial for reducing greenhouse gas emissions. The aim of the study was to fully understand how AM processes influence the mechanical properties of 316L stainless steel when exposed to hydrogen-rich environments.
They found that while AM 316L offered better strength, it showed greater vulnerability to hydrogen embrittlement in pure hydrogen environments.
The Role of Hydrogen in Energy Transition
The growing global shift toward renewable energy has increased interest in hydrogen as a clean alternative fuel. Integrating hydrogen into existing natural gas pipelines presents a cost-effective solution to mitigate greenhouse gas emissions.
However, hydrogen embrittlement, where hydrogen diffuses into metals, reducing ductility and strength, poses significant challenges.
While 316L stainless steel is known for its high resistance to hydrogen embrittlement, the impact of AM on its performance in hydrogen-rich environments is not well understood. This study explores the interaction between AM 316L stainless steel and hydrogen, in support of the safe use of hydrogen.
Evaluating Mechanical Properties
The researchers compared conventionally manufactured (CM) and AM 316L stainless steel to evaluate their performance under hydrogen exposure.
They exposed tensile bars and solubility specimens made from both methods to hydrogen-blended natural gas at 10 MPa, using a 50 % hydrogen blend and 100 % pure hydrogen. Mechanical behavior was assessed through tensile testing, while solubility was measured using hot chemical extraction.
The AM samples were produced via laser-bed powder fusion (LBPF) on an EOS M290 printer, using powder feedstock with particle sizes ranging from 5 to 50 µm. To relieve residual stresses, the printed specimens were heat-treated at 400 °C for one hour.
All AM tensile bars were printed in the vertical build direction, chosen for its higher ductility compared to other orientations. The CM samples were verified for chemical composition using positive material identification (PMI).
The bars were mounted in three-dimensionally (3D) printed holders during testing, placed in carbon steel tubes, and exposed to specified hydrogen environments. After heat exposure they were kept at rest for 72 hours to allow reversible hydrogen degassing before undergoing tensile testing.
Key Findings: Differences in Mechanical Behavior
The study showed clear differences in the mechanical behavior of AM and CM 316L stainless steel under hydrogen exposure. AM samples exhibited higher ductility and yield strength under all conditions when compared to conventionally manufactured 316L.
The AM samples demonstrated an ultimate tensile strength (UTS) of 550 MPa and a yield strength of 480 MPa, while the CM samples showed a UTS of 520 MPa and a yield strength of 450 MPa.
However, prolonged exposure to 100 % hydrogen (pure form) led to a 20 % reduction in ductility and a 15 % increase in yield strength in AM samples, indicating the onset of hydrogen embrittlement. In contrast, CM samples displayed minimal changes in mechanical properties.
Hot extraction analysis confirmed that CM samples retained a higher hydrogen content, mainly due to non-metallic inclusions, such as manganese sulfide, which acted as hydrogen traps.
AM samples, characterized by a refined microstructure and reduced inclusions, demonstrated minimal hydrogen uptake and no significant embrittlement under 50 % hydrogen-blend conditions.
Fractography verified the distinct failure mechanisms observed using scanning electron microscopy (SEM). CM samples exhibited ductile fracture features, while AM samples exposed to pure hydrogen showed quasi-cleavage and brittle fracture surfaces, consistent with hydrogen-induced cracking.
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Some AM samples also displayed oval-shaped cross-sections after failure, evidence of uneven stress distribution caused by localized embrittlement. The presence of micro-voids in AM samples contributed to localized hydrogen accumulation and embrittlement.
The study also identified two important mechanisms contributing to embrittlement in AM 316L: hydrogen-enhanced localized plasticity (HELP) and transformation-induced plasticity (TRIP). These mechanisms, which are influenced by hydrogen interaction with microstructural features, play a key role in the observed reduction in ductility.
Overall, while AM 316L stainless steel shows superior mechanical properties under normal conditions, its unique microstructure can increase susceptibility to hydrogen-related degradation, emphasizing the need for optimized post-processing treatments to enhance its performance.
Practical Applications for Oil and Gas Applications
This research has significant implications for the oil and gas sector, where the integration of hydrogen into existing infrastructure is being explored. While AM 316L stainless steel offers superior mechanical properties, its performance under hydrogen exposure requires careful consideration.
To enhance its suitability for hydrogen-rich environments, the researchers recommend post-processing treatments such as hot isostatic pressing and solution annealing to reduce defects and improve microstructural integrity.
The findings are important for the safe use of AM components in hydrogen service applications, including pipelines and pressure regulators. Understanding the mechanisms of hydrogen embrittlement in AM materials is crucial for developing robust safety protocols.
Conclusion and Future Directions
The study highlights the differences in mechanical properties and hydrogen retention between CM and AM 316L steel samples, emphasizing the associated hydrogen embrittlement issues in AM materials.
The findings underscore the importance of optimizing post-processing techniques to reduce microstructural defects and improve resistance to hydrogen embrittlement. Future work should focus on in situ testing with hydrogen present during mechanical loading, as well as investigate the influence of build orientation on susceptibility to hydrogen embrittlement.
As industries transition toward hydrogen-based energy systems, this research lays the foundation for developing durable AM materials suited for such applications, supporting the broader shift toward a sustainable and low-carbon energy future.
Journal Reference
Gamboa, G., Babakr, A., Young, M, L. (2025). Effect of Hydrogen and Hydrogen-Blended Natural Gas on Additive-Manufactured 316L Stainless Steel in Ambient Oil and Gas Environments. Metals, 15(7), 689. DOI: 10.3390/met15070689, https://www.mdpi.com/2075-4701/15/7/689
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