Electric pulse treatment restores resistance to hydrogen embrittlement in thermally aged duplex stainless steel through G-phase reconfiguration

Abstract

During long-term service in pressurized water reactors, cast duplex stainless steels undergo thermal aging, which promotes the precipitation of nanoscale G-phase particles within the ferrite. Previous studies have suggested that these precipitates can act as reversible hydrogen-trapping sites and may contribute to the increased hydrogen embrittlement susceptibility of thermally aged materials. However, owing to sluggish atomic diffusion, conventional heat treatments have limited ability to regulate the size, morphology, and distribution of G-phase precipitates, thereby restricting the recovery of hydrogen embrittlement resistance in aged materials. To address this issue, the present study compares the effectiveness of electric pulse treatment and isothermal heat treatment at 550 °C for 1 h in restoring resistance to hydrogen-induced plastic damage in specimens aged at 475 °C. Under the applied conditions, isothermal annealing induces only minor modifications to the G phase and provides limited improvement in hydrogen embrittlement resistance. In contrast, electric pulse treatment reduces the G-phase number density from 3.14 × 10 8 to 1.10 × 10 8 mm -2 , decreases the average particle size from 22.09 to 8.56 nm, and promotes the transformation of residual particles from cuboidal to spherical morphologies. After hydrogen charging, the hydrogen embrittlement susceptibility index decreases markedly from 42.86% to 15.79%. Microstructural characterization and secondary-crack analysis further show that electric pulse treatment enhances crack blunting and crack deflection during hydrogen-assisted deformation. These findings indicate that electric pulse treatment offers a feasible low-temperature method for tailoring G-phase precipitates. This technique enhances the resistance to hydrogen embrittlement in thermally aged cast duplex stainless steels.

The authors' abstract, as published at the source. Journal of Materials Research and Technology, 2026 · DOI ↗