What are the classifications of high-temperature alloys?

As a special alloy that can maintain excellent mechanical properties and chemical stability in high temperature environments, high-temperature alloys are classified based on different material characteristics and application requirements, forming a multidimensional classification framework. ​

According to the composition of the matrix elements, high-temperature alloys can be divided into three categories: iron-based, nickel based, and cobalt based. Iron based high-temperature alloys are mainly composed of iron, with the addition of elements such as chromium and nickel to form an austenitic structure. For example, GH2132 alloy has low cost and excellent processing performance, and is suitable for medium temperature conditions. It is commonly used in equipment such as steam turbine blades. Nickel based high-temperature alloys are based on nickel (with a relatively high content) and strengthened by adding elements such as tungsten and molybdenum, which can maintain high strength at higher temperatures. Inconel718 is a typical representative and widely used in aircraft engine turbine discs. Cobalt based high-temperature alloys, such as Haynes25 alloy, excel in sulfur-containing gas environments due to their excellent resistance to heat and corrosion. They are commonly used in the manufacture of combustion chamber components for gas turbines. ​

According to the differences in strengthening mechanisms, high-temperature alloys can be divided into solid solution strengthening type, aging precipitation strengthening type, and oxide dispersion strengthening type. Solid solution strengthening type forms a uniform solid solution by adding elements such as chromium and molybdenum, such as Inconel625, which has good plasticity and weldability and is suitable for manufacturing components such as pipelines that require cold working. Aging precipitation strengthened alloys will precipitate γ ‘phase (such as Ni3Al) at high temperatures, and their strength is significantly improved after aging treatment. GH4169 achieves higher room temperature strength through this mechanism. The oxide dispersion strengthening type impedes dislocation movement through nanoscale oxide particles (such as Y2O3), and MA956 alloy is of this type, with high temperature oxidation resistance far exceeding traditional alloys. ​

According to the classification of forming processes, high-temperature alloys include deformed high-temperature alloys, cast high-temperature alloys, and powder metallurgy high-temperature alloys. Deformable high-temperature alloys, such as GH3030, are made through plastic processing such as forging and rolling, and have a fine grain structure and excellent mechanical properties. They are commonly used in the manufacture of thin-walled pipe fittings. The casting of high-temperature alloys adopts investment casting technology, which can form complex shapes. K418 alloy is a typical casting grade, suitable for irregular components such as turbine blades. Powder metallurgy high-temperature alloys are formed by powder sintering, with uniform composition and no macroscopic segregation. The fatigue strength of FGH96 alloy is significantly improved compared to similar deformed alloys, making it the preferred material for advanced engine turbine discs.
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In addition, it can be further divided into categories such as aerospace, petrochemicals, energy and electricity according to application scenarios. High temperature alloys in the aerospace field emphasize lightweight and instantaneous high-temperature resistance, while alloys used in petrochemicals pay more attention to sulfur corrosion resistance, such as N08810 alloy, which performs excellently in sulfur-containing crude oil processing equipment. This multidimensional classification system not only reflects the material nature of high-temperature alloys, but also provides clear guidance for material selection in different industrial scenarios. With the development of material technology, new types of high-temperature alloys continue to emerge, and the classification system is also continuously enriched and improved, laying an important foundation for the research and application of high-temperature alloys.