Progress in key alloy materials for flue gas turbines: Alloy design, processing, microstructure and properties

Flue gas turbines (FGTs), which are crucial for energy recovery during catalytic cracking, operate under extreme conditions of high temperature, corrosion, erosion, and fatigue. This review summarizes recent advances in key FGT alloy materials, focusing on alloy design, processing, and performance. Nickel-based superalloys such as GH864/GH4738, used for turbine discs and blades, are enhanced by optimizing chemical composition, γ′ precipitates, and grain-boundary carbides to achieve superior microstructural stability and creep resistance. Manufacturing processes leverage large-scale die forging and thermo-mechanical microstructure simulations to produce uniform, large-diameter, nickel-based turbine discs. Cost-effective Fe–Ni–Cr-based alloys (e.g., K213) are used in stator vanes, whereas alloy steel (AISI 4340) shafts are toughened to resist hydrogen embrittlement. Additive manufacturing enables crack-free fabrication and repair of complex blades. Significant progress has been achieved in material systems and component manufacturing. Future efforts require an integrated material–process–property approach and the development of next-generation materials for more demanding service environments to further advance the efficiency and reliability of FGT.