Gadolinium (Gd)-containing stainless steels are promising rack materials for the wet storage of spent nuclear fuel (SNF), as their thermal-neutron absorption capacity and corrosion resistance are critical to safe long-term storage. To address the challenge of simultaneously enhancing neutron absorption and corrosion resistance in Gd-containing stainless steels, this study proposes a synergistic boron–titanium alloying strategy. Three stainless steels, denoted as Gd0.5B0.5, Gd0.5B1.0, and Gd0.5B1.0Ti3.0, were fabricated by powder metallurgy combined with vacuum hot-press sintering (VHPS). The effects of boron (B) and titanium (Ti) additions on the microstructure, neutron absorption capacity, and corrosion behavior in a boric acid environment were systematically investigated. The results show that B addition significantly improves the thermal-neutron absorption capacity of Gd-containing stainless steels. However, it also promotes the precipitation of abundant Cr-rich (Fe, Cr)2B and B-rich (Fe, Mo)3B2 phases in the steel matrix, accompanied by the formation of Cr-depleted zones at the (Fe, Cr)2B/γ interface, thereby deteriorating corrosion resistance. When the B content increased from 0.5 to 1.0 wt pct, both the size and area fraction of the (Fe, Cr)2B and (Fe, Mo)3B2 precipitates increased markedly, while the width of the Cr-depleted zone increased from ~23 to ~40 nm. Accordingly, the corrosion current density increased from 2.64 × 10−7 A/cm2 to 3.42 × 10−7 A/cm2, indicating further degradation of corrosion resistance. After the addition of 3.0 wt pct Ti, the B-containing precipitates were converted to TiB2, and no obvious Cr-depleted zones were observed. Consequently, the corrosion current density decreased from 3.42 × 10−7 A/cm2 to 2.34 × 10−7 A/cm2, and the degree of sensitization decreased from 7.91 to 5.41 pct, demonstrating significantly improved electrochemical stability and intergranular corrosion resistance. Ti addition enhances corrosion resistance by alleviating Cr depletion, mitigating micro-galvanic corrosion, and improving passive film stability. These findings demonstrate that synergistic B–Ti addition is an effective strategy for enhancing both neutron absorption and corrosion resistance in Gd-containing stainless steels, providing guidance for the development of advanced stainless steel rack materials for SNF storage.

Synergistic Boron–Titanium Additions for Dual Enhancement of Neutron Absorption and Corrosion Resistance in Gd-Containing Stainless Steel

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发表日期：

2026年7月24日

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Haibin Li,
Songyuan Ai,
Haohao Zhang,
Mujun Long,
Huamei Duan,
Dengfu Chen,
Danbin Jia

摘要

Gadolinium (Gd)-containing stainless steels are promising rack materials for the wet storage of spent nuclear fuel (SNF), as their thermal-neutron absorption capacity and corrosion resistance are critical to safe long-term storage. To address the challenge of simultaneously enhancing neutron absorption and corrosion resistance in Gd-containing stainless steels, this study proposes a synergistic boron–titanium alloying strategy. Three stainless steels, denoted as Gd_0.5B_0.5, Gd_0.5B_1.0, and Gd_0.5B_1.0Ti_3.0, were fabricated by powder metallurgy combined with vacuum hot-press sintering (VHPS). The effects of boron (B) and titanium (Ti) additions on the microstructure, neutron absorption capacity, and corrosion behavior in a boric acid environment were systematically investigated. The results show that B addition significantly improves the thermal-neutron absorption capacity of Gd-containing stainless steels. However, it also promotes the precipitation of abundant Cr-rich (Fe, Cr)₂B and B-rich (Fe, Mo)₃B₂ phases in the steel matrix, accompanied by the formation of Cr-depleted zones at the (Fe, Cr)₂B/γ interface, thereby deteriorating corrosion resistance. When the B content increased from 0.5 to 1.0 wt pct, both the size and area fraction of the (Fe, Cr)₂B and (Fe, Mo)₃B₂ precipitates increased markedly, while the width of the Cr-depleted zone increased from ~23 to ~40 nm. Accordingly, the corrosion current density increased from 2.64 × 10⁻⁷ A/cm² to 3.42 × 10⁻⁷ A/cm², indicating further degradation of corrosion resistance. After the addition of 3.0 wt pct Ti, the B-containing precipitates were converted to TiB₂, and no obvious Cr-depleted zones were observed. Consequently, the corrosion current density decreased from 3.42 × 10⁻⁷ A/cm² to 2.34 × 10⁻⁷ A/cm², and the degree of sensitization decreased from 7.91 to 5.41 pct, demonstrating significantly improved electrochemical stability and intergranular corrosion resistance. Ti addition enhances corrosion resistance by alleviating Cr depletion, mitigating micro-galvanic corrosion, and improving passive film stability. These findings demonstrate that synergistic B–Ti addition is an effective strategy for enhancing both neutron absorption and corrosion resistance in Gd-containing stainless steels, providing guidance for the development of advanced stainless steel rack materials for SNF storage.