PSI - Issue 54

Lisa Claeys et al. / Procedia Structural Integrity 54 (2024) 250–255 Claeys/ Structural Integrity Procedia 00 (2023) 000 – 000

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dislocations on grain boundaries which aided the decohesion process. At moderate hydrogen concentrations, the HELP mechanism was the dominant one leading to increased slip planarity in the presence of hydrogen with the formation of quasi-cleavage type of fracture as a consequence (Martin, et al., 2011). At larger distance from the edge, the hydrogen concentration dropped as such that none of the mechanisms were able to alter the fracture behaviour anymore. Despite the complex chemistry of the HEA, similar mechanistic interpretation for the hydrogen concentration dependent fracture modes can thus be made as for BCC and FCC steels (Djukic, et al., 2019).

Fig. 5. SE images at different magnification of the fracture surface of a reference specimen.

Hydrogen concentration [wppm]

Hydrogen [wppm]

100 120 140

20 40 60

80

20 µm

0.1

Thickness [mm]

0.2

30 µm

Thickness [mm]

100 µm

50 µm

Fig. 6. SE images at different magnifications of the fracture surface of hydrogen precharged specimens, overlay of the hydrogen concentration profile on the left image. 4. Conclusions The complex chemistry of the high entropy alloy studied in this work resulted in high hydrogen solubility as well as high hydrogen diffusivity compared to FCC 304 stainless steel. The high hydrogen concentration, mainly concentrated at the edge, resulted in a significant embrittlement. A transitional fracture behavior was observed from the edge towards the center of the specimen going from intergranular to quasi-cleavage to ductile microvoid coalescence type of fracture.