Comparative Study of Microstructural Characteristics of P355NH Transporting Pipelines Exposed to Hydrogen

Abstract:

Pipeline transport of hydrogen offers an alternative way to move large volumes of hydrogen from production to use. One method of transport would be to use the infrastructure available for natural gas pipelines, but the specific physical and chemical properties of hydrogen and its degrading effect on metals mean that a different approach to safety considerations is required for practical implementation. Different steel grades show different responses to hydrogen exposure: some microstructures exhibit higher diffusion rates but lower hydrogen solubility, making them more susceptible to degradation. The intensity of this phenomenon depends largely on the microstructure of the steel, its alloy content, and the operating conditions. The aim of this research is to perform a comparative microstructural analysis of the P355NH steel base material and welded joints made using MIG and MIG/TIG welding technologies in pipeline sections with different histories that have been exposed to hydrogen. During the investigation, we used optical microscopic images and hardness maps showing hardness distribution to reveal the characteristics of various material structure details. The study may contribute to optimizing the safety of pipelines used for hydrogen transport and the welding technologies employed, as well as to increasing integrity under hydrogen-loaded operating conditions.

• Periodical: Advances in Science and Technology (Volume 181)
• Pages: 317-328
• DOI: https://doi.org/10.4028/p-eMZ3Mf
• Online since: August 2026
• Authors: Nóra Bencs-Nagy*, János Lukács
• Keywords: Hardness Map, Hydrogen, Microstructural Analysis, Transporting Pipelines, Welded Joint

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