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Grain boundary carbides as hydrogen diffusion barrier in a Fe-Ni alloy: A thermal desorption and modelling study

Published version
Peer-reviewed

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Type

Article

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Authors

Jelita Rydel, J 
Ziętara, M 
Rivera-Díaz-del-Castillo, PEJ  ORCID logo  https://orcid.org/0000-0002-0419-8347

Abstract

© 2018 A significant decrease in hydrogen absorption in the presence of grain boundary carbides compared to the carbide-free microstructure in the Ni-based HR6W alloy was measured by thermal desorption analysis (TDA). This novel observation is at odds with numerous existing reports – precipitate-rich microstructures generally absorb more hydrogen due to trapping effects. This discrepancy can only be explained by grain boundary diffusion which is known to be fast in Ni-based alloys. It is proposed that grain boundary diffusion is hindered by carbides, resulting in decreased hydrogen absorption. Further experimental evidence corroborates the hypothesis. In addition, a diffusion model was developed to quantify the experimental results, incorporating trapping, grain boundary diffusion and temperature effects. It was successfully applied to the reported TDA data as well as additional diffusion data from the literature. A parametric analysis showed that hydrogen absorption scales strongly with grain size and grain boundary diffusivity while grain boundary segregation energy has a much lower impact. The results of the study point at grain boundary precipitation as a possible means of hydrogen embrittlement mitigation in Ni alloys and austenitic stainless steels.

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Keywords

Hydrogen diffusion, Grain boundary diffusion, Carbides, Thermal desorption analysis (TDA)

Journal Title

Materials and Design

Conference Name

Journal ISSN

0264-1275
1873-4197

Volume Title

160

Publisher

Elsevier BV
Sponsorship
Engineering and Physical Sciences Research Council (EP/H022309/1)
Engineering and Physical Sciences Research Council (EP/H500375/1)
Engineering and Physical Sciences Research Council (EP/L014742/1)
Engineering and Physical Sciences Research Council (EP/M005607/1)
EPSRC: EP/H022309/1 and EP/H500375/1 Royal Academy of Engineering for Research Fellowship funding