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

Publikationen: Beitrag in FachzeitschriftArtikelForschung(peer-reviewed)


  • Iman Taji
  • Tarlan Hajilou
  • Daniel Scheiber
  • Shabnam Karimi
  • Werner Ecker
  • Afrooz Barnoush
  • Roy Johnsen
  • V.I. Razumovskiy

Externe Organisationseinheiten

  • Norwegian University of Science and Technology
  • voestalpine Böhler Edelstahl GmbH & Co KG, Kapfenberg
  • Materials Center Leoben Forschungs GmbH


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 nano-voids 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.


FachzeitschriftCorrosion science
Ausgabenummer15 July
StatusVeröffentlicht - 25 Apr 2020