High-temperature technology is essential in many industrial applications, such as aircraft engines and land-based power generation gas turbines. For decades, Ni-based superalloys have been extensively used due to their exceptional high-temperature properties, attributed to the typical morphology of γ’ precipitates coherently embedded in the γ matrix. Demands for high fuel and engine efficiency require the increasing service temperature of superalloys. Although Ni-based superalloys have been evolved by various optimization schemes, their further development hits a bottleneck due to the limitation of the melting point of Ni. The discovery of γ’-Co3(Al,W) precipitates in the Co-Al-W ternary alloys began a new era in the development history of superalloys. Compared with the commercial 1st Ni-based superalloys, the higher melting temperature by 50~150 °C, the greater creep resistance, and the comparative mechanical properties spotlight the novel γ/γ’ Co-Al-W-based research alloys as one of the candidates of high-temperature materials for future generations of advanced propulsion systems.
Since the discovery of γ/γ’ Co-Al-W alloys in 2006, substantial research activities have focused on enhancing all aspects of properties of the 𝛾’ phase and the 𝛾’-strengthened Co-based superalloys mainly in comparison with Ni-based superalloys, including the thermodynamic, physical, mechanical, and environmental properties. However, researches indicate that several drawbacks still restrict the broad applications of Co-Al-W-based superalloys: i) metastable nature of γ’ phase, ii) overhigh mass density (> 9.0 g/cm3) of alloys due to high W contents, iii) narrow γ/γ’ composition range, iv) a low solvus temperature. The alloying treatment is believed to be an efficient way to promote the performance of Co-based alloys. However, the ambiguous underlying mechanism brings great blindness in experiments. Thus, extensive studies on solving these various challenges are still ongoing by exploiting the low-density W-free alloys, parsing the deformation mechanism, computing the thermodynamics and dynamics, understanding the phase stability, establishing the efficient method of alloying design, and so on.
As motivated by the unresolved fundamental issues and promising properties of novel γ/γ’ Co-based superalloys, this Research Topic aims to attract a wide range of sub-themes on the processing, microstructure, and properties of γ/γ’ Co-based superalloys using both state-of-the-art theoretical and experimental techniques. Topics of interest of the Research Topic include, but are not limited to:
• Discovery of low-density γ/γ’ Co-based superalloys
• Microstructure evolution of γ/γ’ Co-based superalloys
• Alloying design based on DFT calculations and machine learning
• Creep and oxidation properties of γ/γ’ Co-based superalloys
• Tuning of mechanical properties of γ/γ’ Co-based superalloys
• Phase stability of γ’ phase
• Plastic deformation behavior of γ/γ’ Co-based superalloys
• Optimization of mechanical properties of γ’ phase
• Thermodynamics and dynamics of γ/γ’ Co-based superalloys
• Advanced processing methods
• Simulation of the deformation process
High-temperature technology is essential in many industrial applications, such as aircraft engines and land-based power generation gas turbines. For decades, Ni-based superalloys have been extensively used due to their exceptional high-temperature properties, attributed to the typical morphology of γ’ precipitates coherently embedded in the γ matrix. Demands for high fuel and engine efficiency require the increasing service temperature of superalloys. Although Ni-based superalloys have been evolved by various optimization schemes, their further development hits a bottleneck due to the limitation of the melting point of Ni. The discovery of γ’-Co3(Al,W) precipitates in the Co-Al-W ternary alloys began a new era in the development history of superalloys. Compared with the commercial 1st Ni-based superalloys, the higher melting temperature by 50~150 °C, the greater creep resistance, and the comparative mechanical properties spotlight the novel γ/γ’ Co-Al-W-based research alloys as one of the candidates of high-temperature materials for future generations of advanced propulsion systems.
Since the discovery of γ/γ’ Co-Al-W alloys in 2006, substantial research activities have focused on enhancing all aspects of properties of the 𝛾’ phase and the 𝛾’-strengthened Co-based superalloys mainly in comparison with Ni-based superalloys, including the thermodynamic, physical, mechanical, and environmental properties. However, researches indicate that several drawbacks still restrict the broad applications of Co-Al-W-based superalloys: i) metastable nature of γ’ phase, ii) overhigh mass density (> 9.0 g/cm3) of alloys due to high W contents, iii) narrow γ/γ’ composition range, iv) a low solvus temperature. The alloying treatment is believed to be an efficient way to promote the performance of Co-based alloys. However, the ambiguous underlying mechanism brings great blindness in experiments. Thus, extensive studies on solving these various challenges are still ongoing by exploiting the low-density W-free alloys, parsing the deformation mechanism, computing the thermodynamics and dynamics, understanding the phase stability, establishing the efficient method of alloying design, and so on.
As motivated by the unresolved fundamental issues and promising properties of novel γ/γ’ Co-based superalloys, this Research Topic aims to attract a wide range of sub-themes on the processing, microstructure, and properties of γ/γ’ Co-based superalloys using both state-of-the-art theoretical and experimental techniques. Topics of interest of the Research Topic include, but are not limited to:
• Discovery of low-density γ/γ’ Co-based superalloys
• Microstructure evolution of γ/γ’ Co-based superalloys
• Alloying design based on DFT calculations and machine learning
• Creep and oxidation properties of γ/γ’ Co-based superalloys
• Tuning of mechanical properties of γ/γ’ Co-based superalloys
• Phase stability of γ’ phase
• Plastic deformation behavior of γ/γ’ Co-based superalloys
• Optimization of mechanical properties of γ’ phase
• Thermodynamics and dynamics of γ/γ’ Co-based superalloys
• Advanced processing methods
• Simulation of the deformation process