1. Introduction to Superalloy
1.1 The high-temperature alloy market has both technical barriers and qualification barriers
High-temperature alloys have strict performance requirements, and the possibility of being replaced by other alloy materials is low. High-temperature alloy mainly refers to metal materials based on iron, nickel and cobalt, which can work for a long time under high temperature above 600°C and certain stress. High-temperature alloys have excellent high-temperature strength, good resistance to oxidation, thermal corrosion, fatigue and fracture toughness. Therefore, there are high technical barriers to R&D and production. Experimental studies have shown that the specific strength of nickel-based alloys is significantly higher than that of aluminum, steel, and titanium alloys at high temperatures, so the possibility of being replaced by other materials is low.
The technical difficulties of high-temperature alloy production are many. As far as deformed superalloys are concerned, production mainly includes three steps: smelting and casting→rough forging and blanking→precision forging and forming; casting high temperature alloys mainly includes two steps of master alloy melting→precision casting; parts blanks produced through the above process It is delivered to the OEM and processed into parts with dimensional accuracy that meets the requirements before being put into use.
The main technical difficulties of superalloy production include:
(1) Alloy strengthening and metallurgical defect control;
(2) Forming and organization control of forgings, especially large forgings have high requirements on equipment and technology;
(3) Casting forming and tissue control technology, etc.
The superalloy market has high qualification barriers. Global high-temperature alloys are mainly used in aerospace, energy and power, petrochemicals, automobiles and other fields, of which the aerospace sector accounts for 55%; followed by the energy and power sector, accounting for 20%; machinery accounting for 10%; metallurgy It accounts for 7%; cars and petrochemicals each account for 3%. For aerospace with extremely high safety performance requirements, the procurement of key raw material superalloys is critical. China's aerospace equipment generally selects suppliers to carry out the research and development of superalloys at the model development stage. Once the equipment is finalized, the procurement channels of its raw materials will not be easily changed, and natural qualification barriers are formed between the participating enterprises and the later entrants, and the orders for the entire service life of the equipment of the model will be exclusively enjoyed.
1.2 China's superalloy industry has entered a new stage of independent research and development
Research on superalloys began in the 1930s, and the need for aeroengines during World War II promoted the development and use of superalloys. British Mond Nickel Company added a small amount of aluminum and titanium to the 80Ni-20Cr alloy to develop the first nickel-based superalloy and used it in turbine engines. Subsequently, the United States launched Vitallium Cobalt-Based Alloy (Co-Cr-Mo) and Inconel Nickel-Based Alloy (Ni-Cr-Fe), which were used in turbochargers and jet engine combustion chambers. In order to continue to improve the high-temperature strength, adding tungsten, molybdenum, cobalt and other elements to the nickel-based alloy to increase the content of aluminum and titanium, developed a series of brands such as Nimonic (Ni-Cr-Ti) in the United Kingdom, Mar-M and IN in the United States Superalloy. The development of cobalt-based and iron-based superalloys is constrained by factors such as lack of resources and high-temperature stability. The Soviet Union began producing nickel-based superalloys of the ЭИ brand in the 1950s, and later produced deformed superalloys of the ЭП series and cast superalloys of the ЖС series. In the 1970s, the United States produced high-temperature alloy components such as oriented crystalline blades, powder metallurgy turbine disks, and single crystal blades to meet the increasing needs of aero engines. So far, the world's high-temperature alloy product series has been perfected. At present, only four countries in the world have formed their own complete superalloy systems, namely China, the United States, Britain and Russia.
Since the successful trial of the first furnace superalloy GH3030 in 1956, the research, production and application of China's superalloys have gone through more than 60 years of development.
The development of high-temperature alloys in China can be roughly divided into three stages:
(1) The first stage: from 1956 to the early 1970s was the initial stage of China's high-temperature alloys, mainly imitating the high-temperature alloys and engine models of the former Soviet Union.
(2) The second stage: from the mid-1970s to the mid-1990s, China's high-temperature alloys were improved, mainly producing European and American models of engines, and the corresponding high-temperature alloy production technology and quality control capabilities were improved.
(3) The third stage: from the mid-1990s to the present, it is a brand-new development stage of high-temperature alloys in China. It mainly applies and develops a batch of new processes, and develops and produces a series of high-performance, high-grade high-temperature alloys. It is equipped with an independently developed domestic engine model.
According to matrix elements, superalloys can be divided into:
(1) Iron-based superalloy;
(2) Nickel-based superalloys, which account for 80% of China's superalloy usage;
(3) Cobalt-based superalloy.
According to the type of alloy strengthening, it can be divided into:
(1) Solid solution strengthening type;
(2) Aged precipitation enhanced type;
(3) Dispersion enhanced type.
According to the molding method, it can be divided into:
(1) Cast high-temperature alloy;
(2) Deformed superalloys, which account for 70% of the usage of Chinese superalloys;
(3) New high-temperature alloys, including powder superalloys, intermetallic compound bases, dispersion-strengthened superalloys, etc.
According to the product type, it can be divided into forgings, rings, bars, plates, pipes, wires and wires.