PSI - Issue 14

Takuya Yoshimoto et al. / Procedia Structural Integrity 14 (2019) 18–25 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Fig. 8. Relationship between hydrogen content of tensile-fractured specimen and mean graphite diameter.

Fig. 9. Relationship between hydrogen content and RRA.

4. Conclusions

The tensile tests of hydrogen-charged ferritic DCIs with different mean graphite diameter were conducted. The effects of hydrogen and graphite size on the hydrogen-induced ductility loss of DCI were investigated and the following conclusions were obtained:  The hydrogen absorption capability of ferritic DCI depended on the mean graphite diameter. There was a critical graphite diameter that increased significantly the hydrogen content of DCI, which was about 13 µm.  The dominant factor affecting the hydrogen-induced ductility loss was hydrogen content. The graphite diameter was nothing more than a factor affecting the hydrogen absorption capability of DCI. Nevertheless, it should be noted that the graphite diameter had an indirect yet significant effect on the hydrogen embrittlement, and this results is important from the viewpoint of microstructural design of DCI.  To control the mean graphite diameter lower than the critical value (13 µm) can be a design guideline for a microstructure of DCI which is resistant to hydrogen.