4.7 Article

Hydrogen assisted intergranular cracking of alloy 725: The effect of boron and copper alloying

期刊

CORROSION SCIENCE
卷 203, 期 -, 页码 -

出版社

PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.corsci.2022.110331

关键词

Hydrogen embrittlement; Nickel-based superalloy; Density functional theory; Micro-scale testing; Atom probe tomography

资金

  1. COMET program within the K2 Center Integrated Computational Material, Process and Product Engineering (IC-MPPE) , Astria [859480]
  2. Equinor, Norway
  3. Voestalpine BO?HLER Edelstahl GmbH Co KG
  4. Research Council of Norway [245963/F50]
  5. Voestalpine BOHLER Edelstahl GmbH Co KG
  6. Austrian Federal Ministries for Climate Action, Environment, Energy, Mobility, Innovation and Technology (BMK) and for Digital and Economic Affairs (BMDW)

向作者/读者索取更多资源

This study aims to improve the hydrogen embrittlement resistance of Alloy 725 through minor alloying modifications. The results show that Mod B alloy exhibits superior resistance to hydrogen embrittlement compared to Mod A alloy by facilitating grain boundary dislocation transfer and generation. Mod C alloy, with the addition of Cu, forms nanovoids in the grain boundaries, but still maintains good resistance to hydrogen embrittlement.
To overcome the Hydrogen embrittlement (HE) susceptibility of the standard Alloy 725 (Mod A), two alloys with minor alloying modifications with B (Mod B) and B+Cu (Mod C) were produced. Then, the intergranular cracking susceptibility was investigated on bi-crystal beams by electrochemical in situ micro-cantilever bending test. The atom probe tomography and first principles calculations were employed to capture and calculate the grain boundary (GB) segregation and its effect on the GB cohesion. Cross-sectional view of the bent beams showed the superior resistance of Mod B against HE by facilitating the GB dislocation transfer/generation. While bending Mod A sample in hydrogen environment leads to form a sharp intergranular cracking, Mod B showed some nano-voids/cracks mostly in dislocation slip bands and rarely in GB path. However, a reduction of strength was observed in load-displacement (L-D) curves of Mod B. The addition of Cu, although not participated in GB segregation, compromised the lost strength of Mod B. In Mod C, after bending in H-charged condition, the nanovoids were formed in GB, but no load drop in L-D curves nor crack propagation in post-deformation observations was detected. The micro-alloying proposed in this study could be an important contribution to the future developing of H resistant alloys via GB segregation engineering.

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