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<p>Stray grain (SG) remains a critical industrial issue in nickel-based single-crystal superalloys. Yet, the precise micro-mechanism of nitrogen-induced SG is still unclear. Therefore, the SG formation mechanism was investigated in alloys with varying Ti (0, 4.1 wt pct) and N (3, 18&#xa0;ppm) contents by directional solidification using a spiral grain selector, characterized by OM, SEM and EBSD, and supported by JMatPro thermodynamic calculation. The results show that SG formation probability reached 94.4 pct in the 4.1Ti–18N alloy but was 0 pct in 4.1Ti–3N and 0Ti–18N alloys. We reveal that TiN itself does not directly induce SG; rather, it acts as potent nucleation site for blocky MC carbides. The growth of these blocky MC carbides induces solute fluctuations and constitutional supercooling, which, coupled with thermal instabilities in the spiral channel, triggers SG nucleation.</p>

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Nitrogen-Induced Stray Grain Formation During Grain Selection in Nickel-Based Single-Crystal Superalloys

  • 期刊论文

  • 发表日期：

    2026年7月12日

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  • Yingjian Zhang,
  • Xin Zhan,
  • Dong Wang,
  • Jian Zhang

摘要

Stray grain (SG) remains a critical industrial issue in nickel-based single-crystal superalloys. Yet, the precise micro-mechanism of nitrogen-induced SG is still unclear. Therefore, the SG formation mechanism was investigated in alloys with varying Ti (0, 4.1 wt pct) and N (3, 18 ppm) contents by directional solidification using a spiral grain selector, characterized by OM, SEM and EBSD, and supported by JMatPro thermodynamic calculation. The results show that SG formation probability reached 94.4 pct in the 4.1Ti–18N alloy but was 0 pct in 4.1Ti–3N and 0Ti–18N alloys. We reveal that TiN itself does not directly induce SG; rather, it acts as potent nucleation site for blocky MC carbides. The growth of these blocky MC carbides induces solute fluctuations and constitutional supercooling, which, coupled with thermal instabilities in the spiral channel, triggers SG nucleation.