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<p>Hot isostatic pressing (HIP) is an established densification technique commonly employed to reduce porosity in cast components. To address the inherent trade-off between porosity healing and grain coarsening during HIP of Inconel 718 (IN718) castings, this study systematically compares the as-cast microstructures and subsequent microstructural evolution and mechanical responses of IN718 alloys produced via vacuum gravity casting (VC) and vacuum centrifugal casting (VCC) under various HIP temperatures (1000–1150&#xa0;°C). The results show that the VCC process, through the application of a directed centrifugal force during solidification, promotes early precipitation of strengthening phases. These precipitates subsequently transform into a continuous grain boundary δ-phase network during HIP, providing effective Zener pinning that significantly inhibits grain growth. In contrast, VC samples require a higher HIP temperature (1150&#xa0;°C) to achieve complete pore closure; however, this leads to pronounced grain coarsening due to the absence of effective pinning structures. Overall, VCC samples demonstrate a synergistic enhancement in pore elimination and grain refinement at a lower HIP temperature (1100&#xa0;°C), maintaining a fine-grained equiaxed structure and exhibiting superior mechanical performance. Specifically, VCC samples processed at 1100&#xa0;°C exhibit a tensile strength of 1178.5&#xa0;MPa and elongation of 21.2% at room temperature, and 1028.6&#xa0;MPa with 30.8% elongation at 650&#xa0;°C. Fracture analysis further reveals that the optimized microstructure in VCC samples promotes ductile fracture via crack deflection at room temperature, while high-temperature deformation is governed by coordinated grain boundary sliding. These results highlight the crucial role of δ-phase stabilization and microstructural uniformity in suppressing intergranular failure and demonstrate that casting-induced microstructure strongly dictates the HIP response. This study offers structure-guided insights for optimizing HIP processing in high-performance IN718 cast components.</p>

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The Effects of Hot Isostatic Pressing on the Solidification Microstructure and Mechanical Properties of Vacuum Precision Cast IN718 Alloy

  • 期刊论文

  • 发表日期：

    2025年11月21日

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  • Minle Liao,
  • Caishi Fang,
  • Chi Zhang,
  • Guohuai Liu,
  • Zhaodong Wang

摘要

Hot isostatic pressing (HIP) is an established densification technique commonly employed to reduce porosity in cast components. To address the inherent trade-off between porosity healing and grain coarsening during HIP of Inconel 718 (IN718) castings, this study systematically compares the as-cast microstructures and subsequent microstructural evolution and mechanical responses of IN718 alloys produced via vacuum gravity casting (VC) and vacuum centrifugal casting (VCC) under various HIP temperatures (1000–1150 °C). The results show that the VCC process, through the application of a directed centrifugal force during solidification, promotes early precipitation of strengthening phases. These precipitates subsequently transform into a continuous grain boundary δ-phase network during HIP, providing effective Zener pinning that significantly inhibits grain growth. In contrast, VC samples require a higher HIP temperature (1150 °C) to achieve complete pore closure; however, this leads to pronounced grain coarsening due to the absence of effective pinning structures. Overall, VCC samples demonstrate a synergistic enhancement in pore elimination and grain refinement at a lower HIP temperature (1100 °C), maintaining a fine-grained equiaxed structure and exhibiting superior mechanical performance. Specifically, VCC samples processed at 1100 °C exhibit a tensile strength of 1178.5 MPa and elongation of 21.2% at room temperature, and 1028.6 MPa with 30.8% elongation at 650 °C. Fracture analysis further reveals that the optimized microstructure in VCC samples promotes ductile fracture via crack deflection at room temperature, while high-temperature deformation is governed by coordinated grain boundary sliding. These results highlight the crucial role of δ-phase stabilization and microstructural uniformity in suppressing intergranular failure and demonstrate that casting-induced microstructure strongly dictates the HIP response. This study offers structure-guided insights for optimizing HIP processing in high-performance IN718 cast components.