PSI - Issue 82

A.H. Jabbari Mostahsan et al. / Procedia Structural Integrity 82 (2026) 169–173 A. H. Jabbari Mostahsan et al. / Structural Integrity Procedia 00 (2026) 000–000

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Fig. 3. Wedge-loaded CT specimen before (left) and after (right) hydrogen charging.

The representative fracture surface that is illustrated in Fig. 4 reveals a sharp boundary between the region of the fatigue pre-crack and the region of the final fracture. Examining the pre-crack length confirmed that the requirements of the ISO 11114-4 (2017) standard with respect to the pre-cracking of specimens were fully met. The fracture surface did not show any microscopic signs of HAC, neither at the tip of the fatigue pre-crack nor inside the region of final fracture. The final fracture was predominantly transgranular, which was most likely attributed to the low-temperature embrittlement of the specimens immersed into liquid nitrogen. Similar observations were made for each of the three CT specimens investigated.

Fig. 4. SEM overview image of a fracture surface (center); detailed images were captured at the interface between the fatigue pre-crack and the region of final fracture (left) and in the region of final fracture (right). 4. Summary and outlook This study investigates the susceptibility of P460QL micro-alloyed steel to hydrogen-assisted cracking (HAC). After storing three wedge-loaded 13 mm-thick compact tension (CT) specimens for 1000 h at the pressure of 200 bar in hydrogen gas, the specimens showed neither any macro- nor any microscopic signs of HAC. Hence, this steel is qualified up to its ultimate tensile strength for manufacturing cylinders that can be used at room temperature at the pressure of 200 bar for storing hydrogen and hydrogen-bearing gases with volumes up to 3000 liters. In a future study the fracture toughness of the steel in gaseous hydrogen will be measured using the J-integral method and the failure mechanism associated with these tests will be discussed.