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<p>This study examines the influence of grain boundary engineering on the susceptibility to liquation cracking in the weld heat-affected zone during fusion welding of 304HCu. Samples of 304HCu were subjected to strain-annealing treatments to optimize the grain boundary character distribution. Liquation cracking susceptibility was evaluated using the spot Varestraint test at 0.5, 1, and 2% augmented strain levels. Results revealed that the as-received (AR) 304HCu exhibited 62% low ∑ coincidence site lattice (CSL) boundaries. A 5% strain imposed through cold rolling followed by annealing at 1323&#xa0;K for 2&#xa0;h resulted in the highest fraction (74%) of low ∑CSL boundaries (hereafter referred to as the GBE sample). The average grain size increased from 7.5&#xa0;to 14&#xa0;µm and 21&#xa0;to 60&#xa0;µm in AR and GBE conditions, considering and excluding twin boundaries as grain boundaries, respectively. Microstructural analysis revealed that the liquation crack density and maximum crack length were higher in the GBE sample compared to the AR sample. This is attributed to the coarser grain structure in the GBE samples, resulting in a reduced total grain boundary area and a lower density of triple junctions, which are critical for arresting crack propagation. The thermal cycle during welding further exacerbated this effect by inducing abnormal grain growth&#xa0;(AGG), which decreased microstructural stability (diminishing low ∑CSL boundaries in the heat-affected zone) and reduced the effectiveness of grain boundaries/triple junctions in resisting liquation cracking.</p>

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Unveiling the Role of Grain Boundary Engineering on Liquation Cracking Susceptibility in 304HCu Superaustenitic Stainless Steel

  • 期刊论文

  • 发表日期：

    2025年6月3日

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  • Vikram Kumar S. Jain,
  • K. V. Phani Prabhakar,
  • V. Subramanya Sarma

摘要

This study examines the influence of grain boundary engineering on the susceptibility to liquation cracking in the weld heat-affected zone during fusion welding of 304HCu. Samples of 304HCu were subjected to strain-annealing treatments to optimize the grain boundary character distribution. Liquation cracking susceptibility was evaluated using the spot Varestraint test at 0.5, 1, and 2% augmented strain levels. Results revealed that the as-received (AR) 304HCu exhibited 62% low ∑ coincidence site lattice (CSL) boundaries. A 5% strain imposed through cold rolling followed by annealing at 1323 K for 2 h resulted in the highest fraction (74%) of low ∑CSL boundaries (hereafter referred to as the GBE sample). The average grain size increased from 7.5 to 14 µm and 21 to 60 µm in AR and GBE conditions, considering and excluding twin boundaries as grain boundaries, respectively. Microstructural analysis revealed that the liquation crack density and maximum crack length were higher in the GBE sample compared to the AR sample. This is attributed to the coarser grain structure in the GBE samples, resulting in a reduced total grain boundary area and a lower density of triple junctions, which are critical for arresting crack propagation. The thermal cycle during welding further exacerbated this effect by inducing abnormal grain growth (AGG), which decreased microstructural stability (diminishing low ∑CSL boundaries in the heat-affected zone) and reduced the effectiveness of grain boundaries/triple junctions in resisting liquation cracking.