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<p>Ni-based superalloy 625 (commercial name Inconel 625—IN625) is primarily strengthened by solid-solution and grain size. However, when IN625 is fabricated <i>via</i> arc-based directed energy deposition (IN625 DED), it develops a coarse microstructure with significant interdendritic segregation (<i>e.g.</i>, Laves phase), which may limit both grain size and solid-solution strengthening, thereby jeopardizing alloy behavior. Attempts to optimize process parameters to control the IN625 DED microstructure have proven ineffective, remaining only the aging-strengthening mechanism (<i>γ</i>″ precipitation) as a plausible approach to enhance IN625 DED performance. In this regard, the present work investigated the aging response of IN625 DED. IN625 DED was homogenized (1150&#xa0;°C/4&#xa0;h) to dissolve the interdendritic precipitates partially. Subsequently, IN625 DED was aged at 650&#xa0;°C, and the aging curve (hardness evolution over time) was established. Aging conditions that met the hardness requirements of API 6ACRA (64, 75, 85, and 108&#xa0;hours) were further evaluated by microstructural analysis and mechanical tests (uniaxial tensile and impact at − 60&#xa0;°C). The proposed heat treatments promoted carbide precipitation at grain boundaries but did not alter the grain stereology or crystallographic texture of IN625 DED. Strength increased with aging time, while absorbed impact energy tends to decrease. All proposed heat treatments satisfied the absorbed impact test energy requirement (100&#xa0;J at − 60&#xa0;°C); however, only the 108&#xa0;hours aged condition met the quasi-static mechanical property requirements specified for wrought Inconel 625 (ASTM B564, UNS N06625 grade 1). Furthermore, none of the tested conditions meets the strength requirements of aged Inconel 625 wrought (API 6ACRA).</p>

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Aging Heat Treatment of Ni-Based Superalloy 625 Fabricated via Arc-Based Directed Energy Deposition

  • 期刊论文

  • 发表日期：

    2026年3月21日

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  • Francisco Werley Cipriano Farias,
  • Hendrick Villela Carrijo,
  • Margareth Nascimento de Souza Lira,
  • João da Cruz Payão Filho

摘要

Ni-based superalloy 625 (commercial name Inconel 625—IN625) is primarily strengthened by solid-solution and grain size. However, when IN625 is fabricated via arc-based directed energy deposition (IN625 DED), it develops a coarse microstructure with significant interdendritic segregation (e.g., Laves phase), which may limit both grain size and solid-solution strengthening, thereby jeopardizing alloy behavior. Attempts to optimize process parameters to control the IN625 DED microstructure have proven ineffective, remaining only the aging-strengthening mechanism (γ″ precipitation) as a plausible approach to enhance IN625 DED performance. In this regard, the present work investigated the aging response of IN625 DED. IN625 DED was homogenized (1150 °C/4 h) to dissolve the interdendritic precipitates partially. Subsequently, IN625 DED was aged at 650 °C, and the aging curve (hardness evolution over time) was established. Aging conditions that met the hardness requirements of API 6ACRA (64, 75, 85, and 108 hours) were further evaluated by microstructural analysis and mechanical tests (uniaxial tensile and impact at − 60 °C). The proposed heat treatments promoted carbide precipitation at grain boundaries but did not alter the grain stereology or crystallographic texture of IN625 DED. Strength increased with aging time, while absorbed impact energy tends to decrease. All proposed heat treatments satisfied the absorbed impact test energy requirement (100 J at − 60 °C); however, only the 108 hours aged condition met the quasi-static mechanical property requirements specified for wrought Inconel 625 (ASTM B564, UNS N06625 grade 1). Furthermore, none of the tested conditions meets the strength requirements of aged Inconel 625 wrought (API 6ACRA).