PSI - Issue 54

Daria Pałgan et al. / Procedia Structural Integrity 54 (2024) 322 –331

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Daria Pałgan et al./ Structural Integrity Procedia 00 (2023) 000 – 000

can diffuse 3-4 orders of magnitude faster in ferrite phase than in austenite phase thus serving as fast diffusion pathways for an increased hydrogen uptake in the 304L steel (Wang et al., 2023). This may be relevant for all charging parameters regardless of type of hydrogen as a higher hydrogen uptake content always were measured for the 304L steel than for the 316L steel.

Figure 4. Effect of a) current density, b) charging time and c) electrolyte temperature on the hydrogen uptake in A516 steel.

Figure 5. Effect of a) current density, b) charging time and c) electrolyte temperature on the hydrogen uptake in 304L steel.

Figure 6. Effect of a) current density, b) charging time and c) electrolyte temperature on the hydrogen uptake in 316L steel.

3.3 Gaseous charging Figures 7 shows the effect of charging time and temperature of gaseous hydrogen charging on the hydrogen uptake for diffusible, trapped, and total hydrogen content for the A516, 304L and 316L steels. From the diagrams in Fig. 7 the effect of charging time and temperature for gaseous hydrogen charging at a pressure of 200 bar in pure H 2 atmosphere could be judged. For the A516 steel an increase of hydrogen uptake was observed for both increased charging time and temperature. However, the hydrogen uptake was more pronounced for trapped hydrogen and very low for the diffusible hydrogen. Note that this trapped hydrogen uptake was more pronounced when charging at 360 °C. In addition, it was observed that irreversible trapped hydrogen seems to reach saturation when charged for times longer than 24 hours. Since the hydrogen peaks at low and high temperature recorded after gaseous charging of 304L and 316L steels were not well separated only the total hydrogen contents below the TDMS curves was evaluated, see Fig. 3a-b. However, similar as for the A516 steel an increased hydrogen uptake was observed with an increased