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<p>Polycrystalline Ni-based superalloy turbine blades fabricated by conventional investment casting often suffer from coarse grains, porosity, and macrosegregation, compromising their reliability under extreme service conditions. In this study, micro-grained K417 superalloy blades were prepared via centrifugal investment casting. The resulting microstructure exhibited uniform cellular dendrites with grain sizes ranging from 26.7 to 31.2&#xa0;μm (ASTM 6) along the radial direction. The γ′ phase was uniformly distributed in cuboidal form within the γ matrix, while γ/γ′ eutectic phases and MC-type carbides were located at grain boundaries. High-temperature tensile tests conducted at 800&#xa0;°C, 900&#xa0;°C, and 1000&#xa0;°C showed ultimate tensile strengths of 946.8&#xa0;MPa, 791.7&#xa0;MPa, and 470.5&#xa0;MPa, respectively, with corresponding elongations of 16.2%, 17.3%, and 22.7%. This transition is attributed to the retention of thermally stable γ′ precipitates and enhanced matrix ductility at elevated temperatures. These factors jointly promote dislocation climb and grain boundary sliding, thereby facilitating ductile fracture modes. Under thermo-mechanical coupling conditions, dynamic recrystallization was significantly suppressed, with DRX fractions remaining below 18% even after 50% strain at 1150&#xa0;°C. This anti-softening behavior was attributed to grain boundary pinning by stable second-phase particles and γ′-mediated strengthening mechanisms, such as dislocation shearing, antiphase boundary formation, and dislocation pair interactions. These findings demonstrate the potential of centrifugal casting for producing high-performance turbine blades with enhanced thermal and mechanical stability.</p>

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Exceptional High-Temperature Tensile Properties and Thermal Stability of Micro-grained Ni-Based Superalloy Turbine Blades via Centrifugal Investment Casting

  • 期刊论文

  • 发表日期：

    2025年7月6日

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  • Minle Liao,
  • Xiaoqing Ma,
  • Chi Zhang,
  • Guohuai Liu,
  • Zhaodong Wang

摘要

Polycrystalline Ni-based superalloy turbine blades fabricated by conventional investment casting often suffer from coarse grains, porosity, and macrosegregation, compromising their reliability under extreme service conditions. In this study, micro-grained K417 superalloy blades were prepared via centrifugal investment casting. The resulting microstructure exhibited uniform cellular dendrites with grain sizes ranging from 26.7 to 31.2 μm (ASTM 6) along the radial direction. The γ′ phase was uniformly distributed in cuboidal form within the γ matrix, while γ/γ′ eutectic phases and MC-type carbides were located at grain boundaries. High-temperature tensile tests conducted at 800 °C, 900 °C, and 1000 °C showed ultimate tensile strengths of 946.8 MPa, 791.7 MPa, and 470.5 MPa, respectively, with corresponding elongations of 16.2%, 17.3%, and 22.7%. This transition is attributed to the retention of thermally stable γ′ precipitates and enhanced matrix ductility at elevated temperatures. These factors jointly promote dislocation climb and grain boundary sliding, thereby facilitating ductile fracture modes. Under thermo-mechanical coupling conditions, dynamic recrystallization was significantly suppressed, with DRX fractions remaining below 18% even after 50% strain at 1150 °C. This anti-softening behavior was attributed to grain boundary pinning by stable second-phase particles and γ′-mediated strengthening mechanisms, such as dislocation shearing, antiphase boundary formation, and dislocation pair interactions. These findings demonstrate the potential of centrifugal casting for producing high-performance turbine blades with enhanced thermal and mechanical stability.