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<p>The as-cast microstructure, physico-chemical properties, mechanical characteristics, and oxidation resistance of the René 77 nickel-based superalloy, produced via lost-wax casting, were analyzed. The experiments included thermodynamic simulations, dilatometry, differential scanning calorimetry (DSC), light and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), scanning-transmission electron microscopy (STEM), hardness and tensile tests, as well as steam oxidation tests. According to DSC analysis, the superalloy began to solidify at 1355&#xa0;°C forming γ matrix dendrites and, during subsequent cooling, the first strengthening phase, namely MC carbides, precipitated directly from the liquid at 1307&#xa0;°C. Dilatometry results indicated that the onset of γ′ dissolution led to a significant increase in the coefficient of thermal expansion above 730&#xa0;°C. The dendritic regions of the casting exhibited a relatively uniform microstructure, characterized by near cube-like secondary γ′ precipitates, with a volume fraction of 27.7% (± 1.9%) and an average size of 0.278&#xa0;μm. In the interdendritic spaces, the secondary γ′ precipitates displayed both a higher volume fraction (42.2% ± 2.1%) and larger mean size (0.493&#xa0;μm). Additionally, eutectic γ − γ′ islands, (Ti, Mo)C carbides, and (Mo, Cr)<sub>3</sub>B<sub>2</sub> borides were detected. The ultimate tensile strength, yield strength and elongation were in the range of 935–1050&#xa0;MPa, 737–762&#xa0;MPa and 3.6–9.3%, respectively.</p>

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Solidification behavior of René 77 nickel-based superalloy produced via vacuum lost-wax casting and its resultant microstructure, strength and oxidation resistance

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年5月25日

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  • Małgorzata Grudzień-Rakoczy,
  • Łukasz Rakoczy,
  • Grzegorz Cempura,
  • Tomasz Dudziak,
  • Ewa Rząd,
  • Konrad Chrzan,
  • Rafał Cygan

摘要

The as-cast microstructure, physico-chemical properties, mechanical characteristics, and oxidation resistance of the René 77 nickel-based superalloy, produced via lost-wax casting, were analyzed. The experiments included thermodynamic simulations, dilatometry, differential scanning calorimetry (DSC), light and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), scanning-transmission electron microscopy (STEM), hardness and tensile tests, as well as steam oxidation tests. According to DSC analysis, the superalloy began to solidify at 1355 °C forming γ matrix dendrites and, during subsequent cooling, the first strengthening phase, namely MC carbides, precipitated directly from the liquid at 1307 °C. Dilatometry results indicated that the onset of γ′ dissolution led to a significant increase in the coefficient of thermal expansion above 730 °C. The dendritic regions of the casting exhibited a relatively uniform microstructure, characterized by near cube-like secondary γ′ precipitates, with a volume fraction of 27.7% (± 1.9%) and an average size of 0.278 μm. In the interdendritic spaces, the secondary γ′ precipitates displayed both a higher volume fraction (42.2% ± 2.1%) and larger mean size (0.493 μm). Additionally, eutectic γ − γ′ islands, (Ti, Mo)C carbides, and (Mo, Cr)3B2 borides were detected. The ultimate tensile strength, yield strength and elongation were in the range of 935–1050 MPa, 737–762 MPa and 3.6–9.3%, respectively.