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Key points: Superalloys, also known as high-temperature alloys, are metal materials capable of operating for extended periods at temperatures above 600°C under certain stress conditions. They possess excellent high-temperature strength, good oxidation and thermal corrosion resistance, as well as superior fatigue resistance and fracture toughness. The material properties of superalloys make them an irreplaceable key material in aeroengines. In the development of advanced engines worldwide, superalloy materials account for 40% to 60% of the total weight of the engines. Therefore, superalloy materials are also known as the “cornerstone of advanced engines”. Superalloys for aeroengines account for more than half of the demand for superalloys. As a number of new models of aero engines in China enter mass production, the demand for superalloys is expected to grow rapidly. Multiple third-and-a-half-generation fighter jets, represented by the J-10B, J-15, and J-16, have been gradually put into service, leading to a continuous increase in the demand for WS-10 engines. In the coming years, with the introduction of the domestically produced large transport aircraft Y-20, high-bypass ratio engines will enter mass production ； Aeroengines with low bypass ratios and moderate thrust, as well as those with low thrust, will also gradually enter mass production. The growing demand for domestically produced aero engines will drive the demand for high-temperature alloys used in aviation into a period of rapid growth. Superalloys are being used more and more widely in the civil industry. Superalloys have important applications in industries such as gas turbines, automotive turbochargers, nuclear power, and the petroleum and petrochemical sectors. The advancement of industrialization and the development of the domestic high-end equipment manufacturing sector will continue to drive demand for superalloys in the civilian industry. At present, civilian applications account for 20% of the total demand for such alloys, and this proportion is expected to rise further in the future. Based on our calculations, we estimate that by 2020, China’s demand for superalloys will be around 40,000 tons, corresponding to a market value of 9.05 billion yuan. The growing demand for superalloys in aviation engines, automotive exhaust turbochargers, and the nuclear power industry will drive a surge in industry demand. Currently, China’s production capacity for superalloys is approximately 12,600 tons, while the actual output is around 8,000–9,000 tons. The compound growth rate of demand for superalloys over the next 7 years is expected to exceed 20%. I. Overview of Superalloys (1) Introduction and Classification to Superalloys Superalloys are a type of metal that can operate for extended periods at high temperatures above 600°C, under certain stresses. What distinguishes superalloys from traditional metals and alloys is their high strength in high-temperature operating conditions, as well as excellent oxidation and thermal corrosion resistance, good fatigue resistance and fracture toughness. They also maintain good structural stability and reliability at various temperatures; in the West, they are also referred to as superalloys. Superalloy materials are the preferred choice for aviation engines, occupying an irreplaceable position in the development of the modern aviation industry. Whether they are produced on a large scale directly determines the level of advancement of aviation equipment. In addition, superalloys are also widely used in the hot-section components of aerospace engines. With the development of industrialization, the demand for superalloy materials in the civilian high-end equipment industry is on the rise. Thanks to their resistance to high temperatures, wear, and corrosion, superalloys are widely used in various civilian industries such as diesel and internal combustion engine turbocharging systems, gas turbines, energy and power generation sectors, petrochemical industries, and the glass and building materials industry. The proportion of superalloys used in these civilian industries has reached around 20%. Superalloys can be classified based on the method of material formation, the types of matrix elements, and the types of alloy strengthening mechanisms: 1) Based on the method of material formation, superalloys can be divided into wrought superalloys, cast superalloys (including conventional precision-cast alloys, directionally solidified alloys, single-crystal alloys, etc.), and powder metallurgy superalloys (including conventional powder metallurgy superalloys and oxide-dispersed strengthening superalloys ODS) ； 2) Based on the type of matrix element, superalloys can be classified into iron-based, nickel-based, cobalt-based, etc ； 3) Based on the type of alloy strengthening, superalloys can be divided into solid solution strengthened superalloys and age-hardening precipitation strengthened alloys. (II) Technical challenges and innovations in superalloy materials: In high-temperature environments, the various rates of material degradation are accelerated; during use, issues such as structural instability, deformation and crack growth under the effects of temperature and stress, as well as oxidative corrosion on the material surface, can occur. The high-temperature resistance, corrosion resistance, and other properties of superalloys mainly depend on their chemical composition and microstructure. Superalloy materials have a very complex composition, containing reactive elements such as chromium and aluminum. In oxidizing or thermochemical corrosion environments, they exhibit chemical stability. However, the surfaces of machined parts suffer from defects such as work hardening and residual stresses, which have a highly adverse effect on both the chemical and mechanical properties of the material. Due to their high degree of alloying, superalloy materials are highly prone to component segregation, and this segregation has a significant impact on the microstructure and properties of both cast and wrought superalloys. These characteristics of superalloys determine the processing techniques that differ from those used for ordinary metal materials. The development of superalloys is a process of continuous improvement and innovation in alloy theory and production technologies, with the material properties of these alloys being enhanced through a combination of alloy strengthening and processing strengthening. Alloy strengthening includes solid solution strengthening of alloys, strengthening by second-phase strengtheners, grain boundary strengthening, etc ； Process intensification involves improving aspects such as smelting, solidification and crystallization, hot working, heat treatment, and surface treatment, in order to enhance the microstructure of the alloy. The production process of superalloys mainly includes three steps: melting, casting, and heat treatment. The manufacturing process has a significant impact on the mechanical properties of superalloy materials. The introduction of a new process often leads to a substantial improvement in the properties of these superalloys, enabling the development of new types of superalloys that in turn contribute to the advancement of a new generation of aircraft engines and airplanes. Older models of alloys can also have their processing improved to enhance their material properties; for example, the use of single-crystal turbine blades has significantly advanced the development of aviation engines. The turbine rotor blades of the F119 engine used in the F-22 are made from third-generation single-crystal superalloy PWA1484; the maximum operating temperature of this material is around 1070°C. By using computational fluid dynamics to design and manufacture supercooled blades, the operating temperature of these turbine rotor blades can be increased to 1621–1677°C (compared to 1400°C for the F100 engine), which illustrates the importance of technological innovation in the development of materials. The preparation technologies and processes for superalloy materials are still undergoing continuous improvement and innovation. For example, the smelting process employs a triple process of vacuum induction + electroslag remelting + vacuum consumable arc melting, and advanced melting control methods are used in vacuum consumable arc melting ； Improving the high strength of materials through directional solidification columnar grain alloy and single crystal alloy processing techniques ； The powder metallurgy method is used to reduce the segregation of alloying elements and improve the strength of the material, among other things. In addition, oxide-dispersed strengthening superalloys and intermetallic high-temperature materials are also continuously evolving and being innovated. II. Applications of superalloys: Research shows that superalloys used in aircraft engines account for over half of the total demand for superalloys. Additionally, they are widely used in industries such as power generation, automotive, and machinery. (1) Aero engines: Known as the “flowers of industry,” aero engines are among the components in the aviation industry that require the highest level of technical expertise and present the greatest challenges to develop. For aero engines, which serve as the power units of aircraft, it is particularly important that the metal structural materials possess properties such as light weight, high strength, high toughness, heat resistance, oxidation resistance, and corrosion resistance – these are practically the highest requirements for structural materials. Technological advancements in aero engines are closely linked to the development of superalloys, which are the most critical structural materials driving the progress of aero engines. Military aviation engines are usually evaluated comprehensively based on their thrust-to-weight ratio (thrust/weight). The most direct and effective technical measure to increase the thrust-to-weight ratio is to raise the gas temperature before the turbine. Therefore, the properties and selection of superalloy materials are key factors determining the performance of aeroengines. With the continuous upgrading of aviation equipment, the requirements regarding the thrust-to-weight ratio of aero engines are constantly increasing; consequently, engines rely more and more on high-performance superalloy materials. In modern advanced aeroengine engines, superalloy materials account for 40%-60% of the total weight of the engine. In aero engines, superalloys are primarily used in four types of heat-exposed components: the combustion chamber, guide vanes, turbine blades, and turbine discs ； It is also used in components such as casings, rings, afterburners, and nozzles. Military aviation engines are generally evaluated based on their thrust-to-weight ratio to determine their performance level. The most direct and effective technical measure to improve the thrust-to-weight ratio is to increase the gas temperature before the turbine. The function of the combustion chamber is to convert the chemical energy of fuel into thermal energy; it is the source of energy for power machinery. The temperature of the gas generated in the combustion chamber ranges from 1500 to 2000°C. The remaining compressed air flows around the combustion chamber, passing through the slots in the chamber walls to keep them cool. The alloy materials used in the combustion chamber can withstand temperatures of 800–900°C or higher, with local temperatures reaching up to 1100°C. The main materials used to manufacture combustion chambers include superalloys, stainless steel, and structural steel ； Among them, the one with the largest usage and the most critical role is the deformation superalloy. Due to the limitation imposed by the melting point of the alloys, traditional superalloy sheets have essentially reached their maximum operating temperature, making further development difficult. To further develop high-temperature alloy materials for combustion chambers, it is necessary to study entirely new material matrices and material preparation processes. Current new materials under international research include carbon/carbon composite materials, high-temperature ceramic materials, oxide-dispersed strengthened alloys, intermetallic compounds, and high-temperature high-strength titanium alloys. Guide vanes are components that adjust the flow direction of the gas exiting the combustion chamber; they are among the parts in an aircraft engine that are subject to the greatest thermal stress. Generally speaking, the temperature of guide vanes is about 100°C higher than that of turbine blades under the same conditions; however, the stress endured by the vanes is relatively low. Following breakthroughs in investment casting technology, casting superalloys has become the primary material for manufacturing guide vanes. In recent years, thanks to the development of directional solidification techniques, the process of using directional alloys to manufacture guide vanes is also under trial ； In addition, an oxide-dispersion-strengthened superalloy was used in the manufacture of the aft labyrinth seal ring of the turbine guide vane for the FWS10 engine. The turbine disk has the greatest mass among the four major hot-end components. When the turbine disc is in operation, the temperature at the rim reaches 550–750°C, while the temperature at the center is only around 300°C; thus, there is a large temperature difference across the entire component ； It experiences significant centrifugal force during rotation ； It experiences high stress and low fatigue cycles during startup and shutdown. The main material used in the manufacture of turbine discs is modified superalloys, among which the G4169 alloy is the most widely used and extensively applied variant. In recent years, as the performance of aero engines continues to improve, higher demands are placed on turbine disks. The advantages of powder-based turbine disks, such as uniform microstructure, fine grains, high strength, and good ductility, make them an ideal alloy for use in aero engine turbine disks. However, the powder turbine disks produced using processes in China contain many impurities, and further research is ongoing to address this issue. Turbine blades are the most critical components in aircraft engines. They operate in extremely harsh conditions, having to withstand high temperatures as well as significant centrifugal stresses, vibration stresses, and thermal stresses. The main material used in turbine blade manufacturing is cast superalloy. Over the past thirty-odd years, with the development of casting techniques, conventional precision casting, directional, and single-crystal casting alloys for blades have been widely used. Single-crystal alloys have seen rapid development on an international scale; five generations of such alloys have been developed, and they have become the primary materials for the high-temperature turbine blades in high-performance commercial aircraft engines ； China began developing single-crystal alloys in the 1980s; according to the monograph \"50 Years of High-Temperature Alloys in China\" by Shi Changxu, second-generation single-crystal alloys are already being used in advanced engines. (II) Aerospace engines: The special operating conditions in aerospace engines require that the materials used must be able to withstand high temperatures, high pressures, large temperature gradients, high dynamic loads, as well as other extreme conditions; as a result, high demands are placed on the comprehensive properties and processability of these materials. Superalloy materials account for a significant proportion in aerospace engines, with their usage accounting for nearly half of the engine’s total weight. The development of superalloy technology has a direct impact on the level of advancement in aerospace engine design. In principle, all high-temperature alloys used for aerospace engines can also be used for aircraft engines. However, in addition to withstanding high-temperature impacts, materials for aerospace engines must also meet requirements related to low-temperature environments (below -100°C). Due to the limitations of the precision casting process for superalloys, structural components with extremely complex shapes have not been truly utilized in aerospace engines in the past. With advances in manufacturing technology, many key thermal components in aerospace engines are now made from precision-cast superalloy parts produced using the shrink-free casting method. This approach simplifies the engine’s structure, reduces its weight, minimizes the need for welding, shortens the development and production cycles, lowers manufacturing costs, and enhances the engine’s reliability. With the advancement of aerospace engine technology, superalloys used in such engines are increasingly showing trends toward complexity, thin walls, compositing, integration of multiple functions, and elimination of waste material. Typical components include a turbine rotor, guide vanes, pump casing, etc. In China’s Long March series of rockets and Shenzhou series of spacecraft, high-temperature alloy materials are used for the core components of their engines. At present, the liquid oxygen-kerosene and liquid oxygen-liquid hydrogen rocket engines, as well as small turbojet and turbofan engines used in the aerospace industry, have been finalized and are now being produced in bulk. The demand in China for high-temperature alloy master alloys and precision castings for aerospace applications is also on the rise, entering a new period of growth. (III) Applications of high-temperature alloys in the civilian industry: With the advancement of industrialization, industries are developing towards higher-end and larger-scale operations; consequently, the demand for high-temperature alloys in the civilian sector is also on the rise. Superalloys are also the preferred materials for turbine blades in ships, trains, cars, as well as for various types of industrial gas turbines ； The acceleration of railway transportation, the high-quality requirements in the shipbuilding industry (especially for export ships), the need for efficient propulsion systems in naval vessels, and the rapid development of industrial gas turbine applications all demand high-performance superalloy master alloys. Currently, high-temperature alloys used in China’s civilian industries account for 20% of the total demand for such alloys, while in the United States, 50% of high-temperature alloys are applied in civilian industrial sectors. Gas turbines represent another major application for superalloys. A gas turbine unit is a rotary thermal engine that uses air and combustion gases as its working medium. Its structure is similar to that of aircraft jet engines, as well as to steam turbines. The basic principle of a gas turbine is similar to that of a steam turbine, with the difference being that the working medium is not steam but the flue gases resulting from fuel combustion. Gas turbines are types of internal combustion engines; therefore, they are also known as internal combustion gas turbines. The structure consists of four main parts: the air compressor, the combustion chamber, the impeller system, and the regenerative device. The demand for gas turbines is growing rapidly; in addition to being used for power generation, they are also employed for ship propulsion and in gas filling stations for natural gas compression. Compared to high-temperature alloy blades used in aviation, those used in gas turbines have a longer service life (100,000 hours), are more resistant to thermal corrosion, are larger in size, and require very high standards in terms of quality. Turbochargers for vehicle exhausts represent another important application area for superalloy materials. At present, the turbine blades used by turbocharger manufacturers in our country are mostly nickel-based superalloy turbine blades, which, together with the turbine shaft and compressor blades, form a rotor. In addition, the valve seats, inserts, intake valves, sealing springs, spark plugs, bolts, and other components of internal combustion engines can be made from iron-based or nickel-based superalloys. The turbocharging system has a significant impact on improving fuel efficiency and performance. Turbocharging utilizes the energy of the exhaust gases expelled by the engine to drive the turbine in the turbine chamber; this turbine in turn drives the coaxial impeller, which forces the air supplied through the air filter ducts to be compressed and sent into the cylinders. As the engine speed increases, the exhaust gas discharge rate and the turbine speed also increase accordingly; the impeller then compresses more air into the cylinders. The increased pressure and density of the air allow for the combustion of more fuel, and by increasing the amount of fuel used, the engine’s output power can be increased. Generally, the power and torque of an engine equipped with a exhaust gas turbocharger increase by 20% to 60%. In 2008, the Chinese automobile industry alone had a demand for high-temperature master alloys for turbine rotors of over 1,900 tons. High-temperature alloys in nuclear power and other fields: The high-temperature alloys used in the nuclear power industry include materials for fuel element cladding, structural materials, and fuel rod holding grids, as well as heat exchangers in high-temperature gas furnaces; these materials are difficult to replace with other alternatives. For example, the wall of the fuel element cladding tube must withstand high temperatures of 600–800°C during operation, which requires high creep strength; therefore, superalloy materials are widely used. Superalloy materials are also widely used in fields such as glass manufacturing, metallurgy, and medical devices. There are more than a dozen types of superalloy components used in the glass industry, such as the centrifugal heads and flame-blowing crucibles used in the production of glass wool, the main shafts, ends, and ventilation pipes of the roll-forming machines used in flat glass production, as well as the material channels, shutters, muffle envelopes, material bowls, and electrode rods in glass furnaces. Shims for heating furnaces in rolling mills in the metallurgical industry, wire rod continuous rolling guides, and thermal electric couple protective sleeves for high-temperature furnaces, etc. Artificial joints and similar products in the field of medical devices. Mengni Alloy mainly produces special materials such as superalloys, nickel-based alloys, copper-nickel alloys, and pure nickel; feel free to reach out if you have any technical inquiries