TY - JOUR

T1 - Hydrogen assisted intergranular cracking of alloy 725

T2 - The effect of boron and copper alloying

AU - Taji, Iman

AU - Hajilou, Tarlan

AU - Ebner, Anna

AU - Scheiber, Daniel

AU - Karimi, Shabnam

AU - Plesiutschnig, Ernst

AU - Ecker, Werner

AU - Barnoush, Afrooz

AU - Maier-Kiener, Verena

AU - Johnsen, Roy

AU - Razumovskiy, V.I.

PY - 2020/4/25

Y1 - 2020/4/25

N2 - 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.

AB - 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.

U2 - 10.1016/j.corsci.2022.110331

DO - 10.1016/j.corsci.2022.110331

M3 - Article

VL - 203.2022

JO - Corrosion science

JF - Corrosion science

SN - 0010-938X

IS - 15 July

M1 - 110331

ER -