Superalloy refers to a kind of metal material based on the third main group elements (iron, cobalt, nickel) and adding a large number of strengthening elements, which can work for a long time under high temperature above 600 °C and certain stress. Superalloys have high high-temperature strength, good oxidation resistance, hot corrosion resistance, fatigue resistance, and good microstructure stability and reliability at high temperatures, so they are also called hot-strength alloys, heat-resistant alloys or superalloys.
After decades of development, Continental has made great progress in the research and production of superalloys, basically forming a high-temperature alloy system with complete grades and forming a certain production capacity. It is a core application material in aerospace, gas turbines, automobiles and other fields.
01
Overview of superalloys
Characteristics of superalloys
Superalloys, also known as heat-resistant alloys and superalloys, refer to metal materials with long-term creep resistance, high strength and corrosion resistance above 600°C and under stress.
Compared with ordinary metals, superalloys have excellent performance in complex working environments: 1) high-temperature strength; 2) antioxidant properties; 3) Resistance to thermal corrosion; 4) fatigue resistance; 5) fracture toughness; 6) The internal organization is stable and reliable to use.
Figure: Superalloys have excellent properties and high properties; Source: New Materials Online
02
Classification of superalloys
Divided according to the constituent elements
高温合金的组成元素主要包括铁（Fe）、镍（Ni）、钴（Co）、钛（Ti）、铝（Al）、铬（Cr）、钼（Mo）、钨（W）等，其中最常见有铁基、镍基、钴基三种。
Iron-based superalloys: superalloys used at moderate temperatures (600-800°C). Iron-based alloys are simple in composition, low in cost, and widely used.
Nickel-based superalloys: nickel-based superalloys used at medium and high temperatures (650-1000°C). Among all superalloys, nickel-based superalloys have the highest high-temperature strength and the widest range of applications. Compared with iron-based alloys, the structure is more stable, the harmful phase is less, and the oxidation and corrosion resistance are stronger.
Cobalt-based superalloys: austenitic superalloys used at high temperatures (730-1100°C) with a cobalt content of 40%-65%. High temperature resistance, but cobalt is a precious metal and its cost is relatively high, limiting the promotion of cobalt-based alloys.
Divided according to the processing method
It can be mainly divided into three categories: deformed superalloys, cast superalloys, and powder metallurgy superalloys.
Deformed superalloy: It refers to a class of alloys that can be processed by hot and cold deformation, with a working temperature range of -253~1320 °C, good mechanical properties and comprehensive strength and toughness indicators, and high corrosion resistance.
Casting superalloys: superalloys that directly prepare parts and components by casting methods. According to the composition of the alloy matrix, it can be divided into three types: iron-based casting superalloys, nickel-based casting superalloys and cobalt-based casting superalloys. According to the crystallization method, it can be divided into four types: polycrystalline casting superalloy, directional solidification casting superalloy, directional eutectic casting superalloy and single crystal casting superalloy.
Powder metallurgy superalloy: a superalloy prepared by powder metallurgy process. Compared with the traditional cast-and-forged superalloys, it has the advantages of uniform structure, no macroscopic segregation, high yield strength and good fatigue resistance.
Divided according to the type of reinforcement
It mainly includes four categories: solution strengthened, precipitation strengthened, oxide diffusion strengthened and fiber strengthened.
Figure: Classification of superalloys; Source: New Materials Online
03
Areas of application of superalloys
Areas of application of superalloys
Due to their outstanding performance in high-temperature operating environments, superalloys are widely used in the core hot-end components of aerospace, aerospace engines, ships and industrial gas turbines. In addition to military use, superalloys also play an irreplaceable role in civilian fields such as electric power, petrochemical industry, automobile, metallurgy, and glass manufacturing.
Figure: Application fields of superalloys; Source: New Materials Online, AVIC Securities Finance Research Institute
Figure: Distribution map of superalloys in various fields; Source: China Business Intelligence Network, China Industry Information Network
The key elements for Hangfa to achieve a breakthrough in performance
Thrust-to-weight ratio, pre-turbine temperature, and fuel consumption rate are the main indicators to measure the performance of aero engines, and they are also an important basis for aero engine generation. The trend for aero engines is to continuously increase thrust-to-weight ratios and pre-turbine temperatures, while reducing fuel consumption. Among them, increasing the pre-turbine temperature helps to improve the thrust-to-weight ratio of the aero engine, and the thrust-to-weight ratio of the aero engine can be increased by about 10% for every 100°C increase in the turbine inlet temperature. From the first generation of aero engines to the current fifth generation of engines, the pre-turbine temperature has increased from the original 1200-1300K to 1850-2000K. With the gradual increase in the temperature before the turbine, the high temperature resistance requirements of the materials used in the combustion chamber are becoming more and more demanding. According to the Journal of Aeronautical Materials, from the mid-60s to the mid-80s of the 20th century, the turbine inlet temperature increased by an average of 15 °C per year, of which the contribution of materials was about 7 °C. Therefore, high-end superalloy materials have become one of the key factors restricting the development of aero engines.
Source: Public information, collected and compiled by AVIC Securities Financial Research Institute
The core raw material for the key components of gas turbines
The basic structure of a gas turbine is similar to that of an aviation gas turbine engine, which is also composed of a compressor, a combustion chamber and a turbine (also known as a gas turbine), with the main difference being that the gas turbine outputs the available work of the gas generator into the torque of the rotor. Gas turbines can be divided into heavy-duty gas turbines and light-duty gas turbines according to their volume and power. Heavy-duty gas turbines are mainly used in the field of power generation, and light-duty gas turbines can be used to power ships, locomotives, tanks and other special vehicles. Gas turbines can also be roughly classified according to the pre-turbine temperature: 900 °C class A, 1000 °C class B, 1100 °C class C class, 1200 °C class D type (such as: M701D), 1300 °C class E type, 1400 °C class F type (such as: M501F/M701F), the use of recovery type steam cooling burner, the inlet temperature of 1500 °C class G type and on this basis also developed 1500 °C class H type (such as: M701H).
Gas turbines have the advantages of small size, light weight, high thermal efficiency, low pollution and low water consumption, and are widely used in shipbuilding, electric power, petrochemical, metallurgy and other fields. The key components of gas turbines, such as turbine working blades and turbine guide vanes, have extremely high requirements for the overall performance of the constituent materials due to the special and complex working environment. Compared with aero engines, gas turbines require superalloys to have unique physical and chemical properties, in addition to good creep strength, fatigue strength and good plasticity:
Extremely strong thermal corrosion resistance, because the working environment of power generation or marine gas turbines is harsher than that of aero engines, and the turbine blades or guide vanes, which are key parts of the hot end, are subject to severe thermal corrosion;
Good tissue stability and long working life. The life of military aircraft engines is usually about a few thousand hours, the life of civil aviation engines is only tens of thousands of hours, and the life of industrial gas turbines requires tens of thousands to hundreds of thousands of hours.
Therefore, superalloy is the core raw material for turbine working blades and guide vanes with excellent processing productivity and stable structure, which directly determines whether the gas turbine can operate efficiently for a long time in complex working environments.
An important material for the manufacture of supercharged turbines for automobiles
Turbocharging technology is gaining traction in the automotive industry because it can significantly increase the torque and power of automobiles, while improving engine efficiency, reducing fuel consumption and reducing exhaust emissions. However, after turbocharging, the pressure and temperature of the engine are greatly increased when working, and due to the high speed, the blade is also subjected to a variety of alternating stresses, so the turbine material is required to have good high-temperature mechanical properties, yield point and long-term microstructure stability and good casting performance. Cast superalloys are widely used in the manufacture of automotive supercharger turbines due to their sufficient strength, thermal stability and good fatigue resistance.
04
Market demand for superalloys
The "two-machine special project" has been accelerated, and the potential demand has increased
The "two aircraft projects" are mainly two major projects of aero engine and gas turbine, and the basic principles of the two engines are the same. In terms of aero engine specialty, it will focus on the field of turbofan and turbojet engine, while taking into account the field of turboshaft, turboprop and piston engine with certain market demand, and mainly develop key products such as large turbofan engines with large bypass ratios, small and medium-sized turbofan/turbojet engines, and medium and high-power turboshaft engines; The main goal of the gas turbine project is to achieve independent development of F-class 300MW gas turbines in 2020 and H-class 400MW gas turbines in 2030. In August 2016, Hangfa Group was formally established, marking the full launch of the two special projects. On April 17, 2017, the Ministry of Industry and Information Technology held the inaugural meeting of the "Two Machines" Basic Research Professional Group in Beijing, and the "Two Machines Special Project" began to accelerate. The full implementation of the "two-engine special project" will promote the localization of Continental aero engines and gas turbines. As one of the key factors that determine the development of the two machines, superalloys will benefit from the implementation of special projects to achieve major breakthroughs, and the potential market space is huge.
Aero engine field
Continental aero engine started late, and the lack of long-term planning for a long time, coupled with the foreign technology blockade, made the development of continental aero engine progress slow, and there is a huge gap of about 30 years with the world's advanced level. In terms of military aircraft engines, the performance indicators of Continental's most advanced WS10 and its improved models are only comparable to those of United States Pratt & Whitney's F100 and General Electric's F110, which are equipped with engines United States for F-15/F-16 fighters that have been in service since the 70s of the last century. Since most of China's engine technology is converted from the former Soviet Union, compared with the United States Pratt & Whitney and General Electric's aero engines, there are significant deficiencies in life and stability, and they usually have to be overhauled after hundreds of hours of flight, which is directly related to the processing technology and performance of the material. In terms of civil aviation engines, China has just started, and the C919, a large commercial mainline aircraft developed by Continental itself, uses the latest generation of LEAP engines jointly developed by United States General Electric and France Safran. Therefore, whether in the field of military or civil aircraft engines, China is still far behind the world's first-class level.
The engine is the "bottleneck" of aircraft development, and the materials and their processing technology are the barriers that directly restrict the development of engines. 60%~70% of advanced military engines with thrust-to-weight ratios of more than 10 and modern civilian engines with large bypass ratios rely on advanced materials and advanced processes. Continental has a large gap with advanced countries such as Europe and the United States in terms of metal materials such as titanium alloy materials and high-temperature alloy materials, as well as non-metallic materials such as ceramic matrix composites, so advanced materials and processing technology are the prerequisites for continuously improving the level of Continental's aero engines. One of the key tasks of the "two-machine special project" is to improve the performance and processing technology of high-end materials such as superalloys and titanium alloys. The R&D and installation of Continental's independent aero engines will open the market ceiling of high-end materials such as superalloys.
Domestic market demand in the field of civil aircraft engines
In the civil aircraft market, Boeing and Airbus, two major aviation giants, have respectively made forecasts for the demand for new aircraft in the next 20 years. According to Boeing's latest "Current Market Outlook" report for the Chinese market released in 2016, it is predicted that China will need 6,810 new aircraft in the next 20 years, with a total value of 1.025 trillion US dollars. Globally, 39,620 new aircraft are needed, with a total value of $5.9 trillion. According to the latest global market forecast released by Airbus at the 2016 Zhuhai Airshow, China will need about 6,000 new passenger and cargo planes worth $945 billion in the next 20 years, and the world needs more than 33,000 new aircraft. Based on the forecast data of the two companies, China's demand for new aircraft is expected to reach about 6,500 in the next 20 years, and the global demand is expected to reach 35,000. Due to the small proportion of ultra-large passenger aircraft, the situation of ultra-large passenger aircraft with 4 engines is not considered here, so it is expected that the global demand for civil aviation engines will reach 70,000 units in the next 20 years, and the domestic market will reach 13,000 units. Currently, the LEAP-1A with a thrust of 32,000 pounds is used by Boeing reaches 7,000 pounds (3,175.147 kg in total) and the LEAP-1B with a thrust of 29,000 pounds is 6,130 pounds (2,780.521 kg in total). Assuming that the engine weight is 3 tons, superalloys account for 50%, and the yield rate is 25%, the global demand for superalloys will reach 420,000 tons in the next 20 years. Although the growth of demand for civil aviation engines will expand the market space for superalloys, because China is still in its infancy in the field of civil aviation engines, the stimulation of the domestic superalloy market is limited.
Figure: Exterior of civil aviation engine; Source: Public information
Market demand in the field of gas turbines
Gas turbines can be divided into heavy-duty gas turbines, light-duty gas turbines and micro-gas turbines according to their structural form.
Heavy-duty gas turbines: the parts are thicker and heavier, requiring a long life, and the mass per unit power is 2~5 kg/kW.
Light gas turbines: Compact components with light weight, with a mass of less than 2 kg/kW per unit of power.
Micro gas turbine: The gas turbine and generator are designed as a whole, which is very small in size and very light in weight.
Figure: Classification of gas turbines; Source: Two-machine power control
Figure: Gas turbine design and structural features; Source: Polaris Power Grid
In the domestic market, gas turbine applications are mainly concentrated in the two major fields of power generation and ships.
In the field of power generation, gas turbine power generation is in a period of accelerated development as the mainland's natural gas resources have entered the stage of large-scale development and utilization. According to the statistics of the High-end Equipment Development Research Center, the main operators of domestic gas turbine power plants are divided into four categories: the first category is the state-owned large-scale power generation central enterprises represented by Huaneng, Huadian and China Power Investment; The second category is provincial power investment groups and energy groups funded and controlled by local governments, such as Zhejiang Energy Group, Shenergy Group, Jingneng Group, etc.; The third category is the self-supplied power plants of domestic iron and steel plants, which use gas for blast furnace gas combined cycle power generation; The fourth category is oil and gas production enterprises, such as CNOOC.
Figure: Types of domestic gas-fired power generation enterprises; Source: Two-machine power control
Although domestic gas-fired power generation is developing rapidly, the vast majority of gas turbines can still only be imported or obtained through cooperation with foreign companies. The main foreign gas turbine suppliers are General Electric (GE), Siemens, Mitsubishi Heavy Industries (MHI) and Alstom (now acquired by GE). Domestic gas turbine suppliers mainly include Shanghai Electric, Dongfang Electric, Harbin Electric and Nanjing steam turbine motors, of which Shanghai Electric cooperates with Siemens, Dongfang Electric partners with Mitsubishi, and Harbin Electric cooperates with Nanqi and GE. As a result, GE's gas turbines account for almost half of the domestic gas turbine market, followed by MHI and Siemens.
The mainland is still in its infancy in the development of gas turbines, and is weak in the market in terms of technology and output. Domestic enterprises that can independently develop gas turbine generator sets include Shenyang Liming Aero Engine Group, Harbin Dongan Engine, AVIC Shixin Gas Turbine Co., Ltd., AVIC Southern Gas Turbine and other companies. The main products include QD128, QD70, QD185 and QD168 series light gas turbines, as well as R0110 heavy gas turbines. At present, it has provided gas turbine products for blast furnace gas combined cycle projects and natural gas distributed energy projects for power plants at home and abroad. With the implementation of the "two-engine special", the self-developed gas turbine is expected to usher in a breakthrough.
In the field of warships, there is a huge gap between the mainland and military powers such as Europe and the United States. At present, foreign modern large and medium-sized surface ships and high-performance ships basically use gas turbines as the main power plant. According to the statistics of foreign ship power plants in 1981~2008, 3/4 of surface ships used gas turbines (including diesel-fuel combined). In contrast, the rate of ship-powered gas turbines of the Continental Army is much lower than that of the old naval powers. At present, the main frigates are powered by diesel engines, and the main destroyers are gradually using diesel-fired hybrids, of which the Type 052 destroyers No. 112 and No. 113 are equipped with American-made LM2500 gas turbines, the Type 052B and 052C destroyers No. 168, 169, 170 and No. 171 are equipped with Ukraine-made GT25000 or domestic imitation models, and the latest 052D destroyers in service use their localized model QC280.
Compared with diesel engines and steam turbines, gas turbines are undoubtedly more in line with the requirements of warships for power system performance, mainly due to the excellent characteristics of gas turbines, such as high success rate, low noise and fast starting speed.
1) Extremely high power density. Normally, the volume of a gas turbine with the same power is 1/3-1/5 of that of a diesel engine and about 1/5-1/10 of a steam turbine. This is determined by the ingenious continuously rotating thermodynamic cycle structure of the gas turbine itself. The gas turbine is small in size and large in power, which is very suitable for the characteristics of small compartments and high speed requirements of warships.
2) Fast start-up speed. Although the engine speed is the highest of the three power systems, the maximum speed can be reached in 1-2 minutes with the help of the starter due to the lightness of the entire rotor. The diesel engine accelerates slowly due to the reciprocating movement of the piston, and the steam turbine is even more "unresponsive", and the starting speed has a direct impact on the combat performance of the warship.
3) Low noise frequency component. Since the gas turbine itself is rotating at high speed and steadily, the noise generated is more of a high-frequency whistling sound. The reciprocating piston of the diesel engine produces a large amount of low-frequency mechanical vibration noise, which just caters to the characteristics of low-frequency noise that is easy to spread in the ocean, resulting in warships being easily detected by enemy sonar. Therefore, diesel engine power is particularly unsuitable for anti-submarine warships as a power system.
Judging from the development path of the old naval powers such as the United States, Japan, and Europe, the use of gas turbines as the power of warships is an inevitable trend under the upgrading of warships in the future. In recent years, the mainland has accelerated the updating of the navy's modern equipment, and all kinds of new ships have been launched into service like dumplings, which has brought new development opportunities to the relevant industrial chain while continuously improving the strength of our navy, especially the suppliers of upstream high-end materials and parts. The demand for superalloys, which are indispensable key materials for the production of gas turbines, is also rising.
Market demand in other fields such as automobiles
With people's pursuit of automobile power and environmental protection, small-displacement turbocharged vehicles are gradually sought after. At present, the use of exhaust gas turbochargers in modern diesel engines has been very common, and the application in gasoline engines is also accelerating, and the number of models with "T" on the market is gradually increasing, and the turbocharger market continues to expand. According to the statistics of China's industrial research report, the use of turbocharging technology for medium and heavy-duty trucks and buses in mainland China has been close to 100%, and the use of turbocharging technology for light trucks and buses is close to 80% of the level, with the increase in the application proportion of small and medium-sized superchargers in passenger cars, construction machinery, some marine machinery and other fields, the annual demand for turbochargers can reach more than 2 million units, and the demand for superalloys has increased steadily.
In the future, with the implementation of the two-machine special project and the continuous growth of the turbocharged vehicle market, the domestic market of superalloys will show a trend of sustained and steady growth.
05
The current state of supply of superalloys
The system is complete and the gap between supply and demand is large
After decades of development, Continental has made great progress in the research and production of superalloys, basically forming a high-temperature alloy system with complete grades and forming a certain production capacity. However, compared with United States, Russia and other countries, there is still a large gap in the technical level and production scale of superalloys.
There are two main categories of domestic manufacturers engaged in superalloys:
The first category is special steel manufacturers, such as Fushun Special Steel, Baosteel Special Steel and Panchang Steel, superalloy is only a small part of its special steel business, relatively weak in talent reserve and R&D capabilities, and relatively single products;
The second category is scientific research units and their subordinate enterprises: such as the General Iron and Steel Research Institute (Steel Research Institute Gaona), Beijing Institute of Aeronautical Materials, Shenyang Institute of Metals, Chinese Academy of Sciences (Zhongke Sannai), with strong research and development capabilities, complete product categories and leading technology, but its special scientific research attributes make the production capacity relatively small.
At present, nearly 300,000 tons of superalloy materials are consumed in the international market every year, and the annual demand of the mainland is more than 20,000 tons, with a market size of more than 8 billion. The total production capacity of the main manufacturers of superalloys in mainland China is about 12,800 tons, and the actual output is only about 10,000 tons, of which Fushun Special Steel and Steel Research Gaona occupy the majority. In the future, with a large number of new demand brought about by the implementation of the two-machine project, the consumption of superalloys in mainland China will increase rapidly. Due to the high technical threshold of superalloys, especially high-end superalloys that require fine processing, the cycle of expanding production capacity is long and difficult, so it is difficult for output to keep up with the growth of demand in the short term, and the gap between supply and demand will be further expanded.