A growing economy relying on hydrogen as a renewable energy source requires improved understanding and control of hydrogen environment embrittlement (HEE) of construction parts for hydrogen storage, transport and power conversion. Thereby, austenitic stainless steels of AISI type 316L are among the most reliable and widely used structural materials. They offer high resistance to corrosion, oxidation, stress corrosion cracking and excellent tensile ductility. Moreover, they possess an inherently lowered HEE susceptibility compared to a variety of other steel grades. Complementary, additive manufacturing (AM) of steel parts offers significant advantages in the production process, enabling near net shape manufacturing of complex geometries from CAD files, reducing post-production steps. Furthermore, AM316L with its resulting characteristic hierarchical defect structure strongly enhances the steels’ strength, allowing for weight reduction of construction parts.

However, the AM defect structure is also prone to hydrogen embrittlement. Hence, to apply AM316L in hydrogen environments its HEE susceptibility must be characterized and optimized. In this contribution [1] we investigate effects of strain-induced twins and martensite on the hydrogen embrittlement of AM316L under tension in the temperature window from 80 K to 300 K. It is revealed that the observed increased HEE susceptibility of this steel grade is related to the quasi-cleavage of twin boundaries as the major path of material failure. On the other hand, strain-induced martensite is shown to have a low impact on the H-embrittlement of AM316L, since it emerges only late in the deformation process in crack regions of largest strain. From this, a model of the hydrogen embrittlement mechanisms active in AM316L and possible routes for its reduction are proposed.

References

[1] Y. Hong, C. Zhou, S. Wagner, S. Schlabach, A. Pundt, L. Zhang, J. Zheng, Corrosion Science, 2022, 208, 110669-1-16.