The definition of superalloy is expounded.

Definition of scientific and technological terms

English name: definition of superalloy: refers to the alloy with certain mechanical properties, oxidation resistance and corrosion resistance at the temperature above 650℃, which is often referred to as nickel-based, iron-based and cobalt-based superalloys at present. Discipline: aviation technology (first-class discipline); Aviation Materials (two disciplines) This content is approved and published by the National Committee for the Examination and Approval of Scientific and Technical Terminology.

printing block

Superalloy is an alloy that can bear certain stress at 600- 1200℃ and has oxidation resistance or corrosion resistance.

catalogue

brief introduction

develop

Improve strength, solid solution strengthening

Precipitation strengthening

grain boundary strengthening

Oxide dispersion strengthening

manufacturing process

development trends

technological development

Brief introduction of material application

develop

Improve strength, solid solution strengthening

Precipitation strengthening

grain boundary strengthening

Oxide dispersion strengthening

manufacturing process

development trends

technological development

Material application

Expand and edit this introduction.

According to the matrix elements, it can be divided into superalloy, nickel-based superalloy and cobalt-based superalloy. According to the preparation process, it can be divided into deformed high temperature and high temperature alloy.

Alloy, cast superalloy and powder metallurgy superalloy. According to the strengthening methods, there are solid solution strengthening, precipitation strengthening, oxide dispersion strengthening and fiber strengthening. Superalloys are mainly used to manufacture high-temperature components such as turbine blades, guide vanes, turbine disks, high-pressure compressor disks and combustion chambers of aviation, ships and industrial gas turbines, and also used to manufacture energy conversion devices such as aerospace vehicles, rocket engines, nuclear reactors, petrochemical equipment and coal conversion.

Edit this paragraph to develop.

Development process Since the late 1930s, Britain, Germany, the United States and other countries began to study superalloys. During World War II, in order to meet the needs of new aero-engines, the research and application of superalloys entered a period of vigorous development. In the early 1940s, a small amount of aluminum and titanium were added to 80Ni-20Cr alloy for the first time in Britain to form γ phase for strengthening, and the first nickel-based alloy with higher high temperature strength was developed. At the same time, in order to meet the needs of the development of piston aero-engine turbocharger, the United States began to manufacture blades with Vitallium cobalt-based alloy. In addition, the United States also developed Inconel to manufacture the combustion chamber of jet engines. Later, IN order to further improve the high-temperature strength of the alloy, metallurgists added tungsten, molybdenum, cobalt and other elements to the nickel-based alloy to increase the content of aluminum and titanium, and developed a series of brands of alloys, such as "Nimonic" in Britain, "Mar-M" and "IN" in the United States. Superalloys such as nickel and tungsten are added to cobalt-based alloys.

Elements, developed a variety of high-temperature alloys, such as X-45, HA- 188, FSX-4 14 and so on. Due to the lack of cobalt resources, the development of cobalt-based superalloys is limited. In the 1940s, superalloys were also developed. In 1950s, brands such as A-286, Incoloy90 1 appeared. However, due to poor high-temperature stability, it has developed slowly since the 1960s. The Soviet Union began to produce "эи" brand nickel-based superalloys around 1950, and later produced "эп" series wrought superalloys and с series cast superalloys. In China, the trial production of superalloys began with 1956, and gradually formed "GH" series wrought superalloys and "K" series cast superalloys. In the 1970s, the United States also adopted new production technology to manufacture directionally crystallized blades and powder metallurgy turbine disks, and developed high-temperature alloy components such as single crystal blades to meet the needs of increasing inlet temperature of aero-engine turbines. Beijing Rongpin Technology Co., Ltd. provides high-temperature alloy forgings.

Edit this paragraph to improve the strength.

solution concentration

Add elements (chromium, tungsten, molybdenum, etc. ) The atomic size different from that of the matrix metal leads to the lattice distortion of the matrix metal.

Adding elements (such as cobalt) that can reduce the stacking fault energy of alloy matrix and elements (such as tungsten and molybdenum) that can slow down the diffusion rate of matrix elements to strengthen the matrix.

Precipitation strengthening

Through aging treatment, the second phase (γ, γ ",carbide, etc.). ) precipitates from supersaturated solid solution to strengthen the alloy. The γ phase is the same as the matrix, which is a face-centered cubic structure, and its lattice constant is close to that of the matrix, which is the same as that of the crystal. Therefore, γ phase can be uniformly precipitated in the matrix in the form of fine particles, which hinders dislocation movement and has a significant strengthening effect. γ phase is A3B intermetallic compound, A stands for nickel and cobalt, B stands for aluminum, titanium, niobium, tantalum, vanadium and tungsten, while chromium, molybdenum and iron can be both A and B. The typical γ phase in nickel-based alloys is Ni3(Al, Ti). The strengthening effect of γ phase can be enhanced by the following ways: ① increasing the number of γ phase; (2) There is a proper mismatch between γ phase and matrix to obtain the strengthening effect of lattice distortion; (3) Adding Nb, Ta and other elements to increase the antiphase domain boundary energy of γ phase, thus improving the dislocation cutting resistance of its superalloy.

Force; ④ Adding elements such as cobalt, tungsten and molybdenum to improve the strength of γ phase. γ "phase is a body-centered cubic structure, and its composition is Ni3Nb. Because of the large mismatch between γ "phase and matrix, it can cause a large degree of lattice distortion and make the alloy obtain a high yield strength. But above 700℃, the strengthening effect is obviously reduced. Cobalt-based superalloys generally do not contain γ phase, but are strengthened with carbides.

grain boundary strengthening

At high temperature, the grain boundary of the alloy is the weak link, and the grain boundary strength can be improved by adding trace amounts of boron, zirconium and rare earth elements. This is because rare earth elements can purify grain boundaries, boron and zirconium atoms can fill grain boundary vacancies, reduce grain boundary diffusion rate during creep, inhibit grain boundary carbide aggregation and promote grain boundary second phase spheroidization. In addition, the strength and plasticity of grain boundaries can also be improved by adding proper amount of hafnium to the casting alloy. It is also possible to form chain carbides or bend grain boundaries by heat treatment to improve plasticity and strength.

Oxide dispersion strengthening

By powder metallurgy, fine oxides which are stable at high temperature are added to the alloy, which is a kind of dispersed super alloys.

State, so as to obtain a significant strengthening effect. Commonly added oxides are ThO2 and Y2O3. These oxides strengthen the alloy by preventing dislocation movement and stabilizing dislocation substructure.

Edit the manufacturing process in this section.

Superalloys containing little or no aluminum and titanium are generally melted by electric arc furnace or non-vacuum induction furnace. When the superalloy containing aluminum and titanium is melted in the atmosphere, the burning loss of elements is difficult to control, and more gases and inclusions enter, so vacuum melting should be adopted. In order to further reduce the content of inclusions, improve the distribution of inclusions and the crystal structure of ingots, a duplex process combining melting and secondary remelting can be adopted. The main means of smelting are electric arc furnace, vacuum induction furnace and non-vacuum induction furnace; The main means of remelting are vacuum consumable furnace and electroslag furnace. high-temperature alloy

Forging cogging can be used for solid solution strengthening alloys and alloy ingots with low aluminum and titanium content (the total amount of aluminum and titanium is less than 4.5%); Alloys with high aluminum and titanium content are generally extruded or rolled into blanks, and then hot rolled into products, and some products need further cold rolling or cold drawing. Alloy ingots or cakes with larger diameter need to be forged by hydraulic press or rapid forging hydraulic press. At present, precision casting is widely used in alloys with high alloying degree and difficult deformation, such as casting turbine blades and guide blades. In order to reduce or eliminate grain boundaries and pores perpendicular to the stress axis in cast alloys, directional crystallization technology has been developed in recent years. In this process, grains grow along the crystallization direction during the solidification of the alloy to obtain parallel columnar crystals without transverse grain boundaries. The first technological condition to realize directional crystallization is to establish and maintain a large enough axial temperature gradient and good axial heat dissipation conditions between liquidus and solidus. In addition, in order to eliminate all grain boundaries, it is necessary to study the manufacturing process of single crystal blades. Powder metallurgy process is mainly used to produce precipitation strengthened and oxide dispersion strengthened superalloys. This process can make the cast superalloy which can not be deformed generally obtain plasticity or even superplasticity. The properties of comprehensively treated superalloys are closely related to their microstructure, which is controlled by metal heat treatment. Superalloys usually require heat treatment. Precipitation strengthened alloys are usually treated by solution treatment and aging treatment. Solution-strengthened alloys are treated only by solution treatment. Some alloys must undergo one or two intermediate treatments before aging treatment. First of all, the solution treatment is to make the second phase dissolve into the alloy matrix, thus alloying at high temperature.

Strengthening phases such as γ and carbide (cobalt-based alloy) are uniformly precipitated during aging treatment. Secondly, appropriate grain size is obtained to ensure high-temperature creep and durability. The solution treatment temperature is generally 1040 ~ 1220℃. At present, most widely used alloys are intermediate treated at1050 ~1100℃ before aging treatment. The main function of intermediate treatment is to precipitate carbides and γ films at grain boundaries and improve the state of grain boundaries. At the same time, some alloys also precipitate some large γ phases, which form a reasonable combination with the fine γ phases precipitated during aging treatment. The purpose of aging treatment is to uniformly precipitate γ phase or carbide (cobalt-based alloy) from supersaturated solid solution to improve high temperature strength. The aging temperature is generally 700 ~ 1000℃.

Edit the development trend of this paragraph

The development trend of superalloys is to further improve the working temperature of alloys, improve the ability to bear various loads at medium and high temperatures, and prolong the service life of alloys. As far as turbine blade materials are concerned, single crystal blades will enter the practical stage, and the comprehensive performance of directional crystallization blades will be improved. In addition, quenched alloy powder can also be used to manufacture multi-layer diffusion-connected hollow blades to meet the needs of gas temperature rise. As far as the materials of guide vane and combustion chamber are concerned, the alloy strengthened by oxide dispersion can be used, which greatly improves the service temperature. In order to improve the corrosion resistance and wear resistance, the protective coating materials and technology of the alloy will also be further developed.

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Microstructure and properties of high gradient directionally solidified * * * crystal superalloy K4 169 Study on microstructure refinement and properties optimization of superalloy.

Directional Dissolution and Transformation of ni5zr in Cast Nickel-based Superalloy and Effect of Hafnium Content on Nickel-based Superalloy: Effect of Magnesium on Superalloy GH220: Study on the Second Phase of GH2027 Superalloy: Study on Adding Carbide Particles in Ni_3Al-based Superalloy: Precipitation of MC and M3B _ 2 Phase in Nickel-Chromium-Cobalt Superalloy. Study on high temperature and low cycle fatigue behavior of GH4 145/SQ Transformation in forming quality control of deformed superalloys: Group superalloys with high gradient directional solidification of * * * crystal superalloys.

Study on Microstructure Refinement and Property Optimization of K4 169 Superalloy: Dissolution and orientation transformation process of ni5zr in cast nickel-based superalloys and influence of hafnium content on nickel-based superalloys: Role of Mg in GH220 Superalloy: Microstructure and phase analysis of FGH95 powder superalloys during stress aging: Microstructure and γ′ phase precipitation of Rene'88DT powder superalloys. Mechanical study on crack initiation and propagation behavior caused by inclusions in nickel-based powder superalloy

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Superalloy is a kind of metal material based on iron, nickel and cobalt, which can work for a long time at high temperature above 600℃ and under certain stress. It has high high temperature strength, good oxidation and corrosion resistance, good fatigue performance, fracture toughness and other comprehensive properties. Superalloy is a single austenite structure, which has good structural stability and reliability at various temperatures.

Based on the above properties and characteristics, superalloys with high alloying degree, also known as "superalloys", are important materials widely used in aviation, aerospace, petroleum, chemical industry and ships. According to the matrix elements, superalloys can be divided into iron-based, nickel-based and cobalt-based superalloys. Generally, the service temperature of superalloys can only reach 750~780℃. For heat-resistant parts used at higher temperatures, alloys based on nickel and refractory metals are used. Nickel-based superalloys occupy a particularly important position in the whole field of superalloys, and are widely used to manufacture the hottest parts of aviation jet engines and various industrial gas turbines. If the endurance strength of 150MPA- 100H is taken as the standard, the maximum temperature that nickel alloy can withstand at present is > 1 100℃, while nickel alloy is about 950℃ and iron-based alloy is less than 850℃, that is, nickel-based alloy is higher than 150℃ correspondingly. So people call nickel alloy the heart of the engine. At present, in advanced engines, nickel alloy has accounted for half of the total weight. Not only turbine blades and combustion chambers, but also turbine disks and even compressor blades in the last few stages began to use nickel alloys. Compared with ferroalloy, nickel alloy has the advantages of high working temperature, stable structure, less harmful phases and strong oxidation and corrosion ability. Compared with cobalt alloy, nickel alloy can work under higher temperature and stress, especially in moving blades. The above advantages of nickel alloy are related to some excellent properties of nickel alloy. Nickel is a face-centered cube with a high structure. Vacuum furnace is the key equipment for producing superalloy.

Stable, no allotropic transition from room temperature to high temperature; This is very important for the selection of matrix materials. As we all know, austenite structure has a series of advantages over ferrite structure. Nickel has high chemical stability, hardly oxidizes below 500℃, and is not affected by hot gas, water and some brine solutions at theoretical temperature. Nickel dissolves slowly in sulfuric acid and hydrochloric acid, but rapidly in nitric acid. Nickel has great alloying ability, even if more than ten alloying elements are added, there is no harmful phase, which provides potential possibilities for improving various properties of nickel. Although the mechanical properties of pure nickel are not strong, its plasticity is excellent, especially at low temperature.