Jeong, H., Jeong, J. Y., Lee, S. Y., Ryou, K., Choi, P.-P., Zhao, Y., Wei, S., Wang, P., & Lee, D.-H. (2025). Effect of boron segregation on hydrogen-induced grain boundary embrittlement in CoCrFeNi medium-entropy alloys. Corrosion Science, 257, 113320. https://doi.org/10.1016/j.corsci.2025.113320
Abstract:
Hydrogen embrittlement (HE) degrades the mechanical performance of metals in hydrogen
environments, posing challenges to the safety and reliability of hydrogen energy systems.
Although face-centered cubic (FCC) high-/medium-entropy alloys (H/MEAs) show promise
due to their intrinsic HE resistance, intergranular failure still occurs under extreme conditions.
This study investigated the effect of boron doping on hydrogen-induced grain boundary (GB)
embrittlement in CoCrFeNi MEAs under as-cast conditions. Approximately 80 wt. ppm boron
was added without altering the microstructure of the alloy. In situ hydrogen-charging tensile
tests revealed that boron doping significantly reduced ductility loss, with the HE index
decreasing from ~82% to ~32%, and shifted the fracture mode from intergranular to
transgranular. Atom probe tomography confirmed selective boron segregation at the GBs.
Thermal desorption spectroscopy and Ag decoration experiments demonstrated that boron
suppressed hydrogen trapping at GBs by occupying interstitial sites. Spherical nanoindentation
showed decreased critical shear stress for GB slip transmission in the boron-doped alloy,
suggesting enhanced GB plasticity. These combined effects—strengthened GB cohesion,
reduced hydrogen accumulation, and improved slip transmission—synergistically contributed
to the enhanced HE resistance of the boron-doped CoCrFeNi MEA.
License type:
Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Funding Info:
This research / project is supported by the A*STAR - Development of High- Performance Electric Traction Module HiPe E-TraM,
Grant Reference no. : M22K4a0044