Development of high temperature alloy materials
author: www.qishine.com
2025-01-18
High-temperature alloy materials generally refer to alloy materials that work under certain stress conditions above 600°C.
It not only needs to have good high-temperature oxidation resistance and corrosion resistance, but also has high high-temperature strength, creep strength, endurance performance and good fatigue resistance.
It is a key hot end component material for modern aircraft engines, spacecraft and rocket engines, as well as ships and industrial gas turbines (such as turbine blades, guide vanes, turbine discs, combustion chambers and casings, etc.). It is also an important high-temperature material required by the petroleum and natural gas industry, chemical equipment and coal conversion technology equipment.
1. Development process of high temperature alloy materials
Nickel-based superalloys were developed in the late 1930s. The following is the production time of nickel-based superalloys in various countries:
1) 1941: Britain first produced the nickel-based alloy Nimonic 75 (Ni-20Cr-0.4Ti); in order to increase the creep strength, aluminum was added and Nimonic 80 (Ni-20Cr-2.5Ti-1.3Al) was developed.
Nickel-based superalloys were developed in the late 1930s. The following is the production time of nickel-based superalloys in various countries:
1) 1941: Britain first produced the nickel-based alloy Nimonic 75 (Ni-20Cr-0.4Ti); in order to increase the creep strength, aluminum was added and Nimonic 80 (Ni-20Cr-2.5Ti-1.3Al) was developed.
2) Mid-1940s: United States
3) Late 1940s: Soviet Union
4) Mid-1950s: China
Two aspects of the development of nickel-based alloys
Including: Improvement of alloy composition and innovation of production process
Early 1950s: The development of vacuum melting technology created conditions for the refining of nickel-based alloys containing high aluminum and titanium. Most of the early nickel-based alloys were deformed alloys.
Including: Improvement of alloy composition and innovation of production process
Early 1950s: The development of vacuum melting technology created conditions for the refining of nickel-based alloys containing high aluminum and titanium. Most of the early nickel-based alloys were deformed alloys.
Late 1950s: Using investment casting technology, a series of casting alloys with good high-temperature strength were developed.
Mid-1960s: Development of directional crystallization and single crystal high-temperature alloys and powder metallurgy high-temperature alloys with better performance.
In order to meet the needs of ships and industrial gas turbines, a number of high-chromium nickel-based alloys with good thermal corrosion resistance and stable structure have been developed since the 1960s.
From the early 1940s to the late 1970s, the operating temperature of nickel-based alloys increased from 700°C to 1100°C, an average increase of about 10°C per year.
2. Classification
According to the manufacturing process, high-temperature alloy materials can be divided into deformed high-temperature alloys, cast high-temperature alloys, powder metallurgy high-temperature alloys and divergent cooling high-temperature alloys.
According to the alloy matrix elements, they can be divided into iron-based, nickel-based and cobalt-based high-temperature alloys. The most widely used is nickel-based high-temperature alloy, which has the highest high-temperature endurance strength, followed by cobalt-based high-temperature alloy, and iron-based high-temperature alloy has the lowest.
According to the strengthening method, it can be divided into solid solution strengthened high temperature alloys, aging strengthened high temperature alloys and oxide dispersion strengthened high temperature alloys.
According to the main use, it can be divided into plate alloy, rod alloy and disc alloy.
Nickel-based deformed high-temperature alloy
(wrought nickel -base superallo)
(wrought nickel -base superallo)
A deformable high-temperature alloy with nickel as the main matrix component. Chinese nickel-based deformable high-temperature alloys are represented by the Chinese phonetic letter "GH" plus a serial number, such as GH36, GH49, GH141, etc. It can be processed into materials by conventional cold and hot deformation methods such as forging, rolling and extrusion.
According to the strengthening method, it can be divided into three categories: solid solution strengthened nickel-based deformable high-temperature alloy, weak aging strengthened nickel-based deformable high-temperature alloy and strong aging strengthened nickel-based deformable high-temperature alloy.
Application: Nickel-based deformed high-temperature alloys are widely used to manufacture hot end components of aviation jet engines and various industrial gas turbines, such as working blades, guide blades, turbine disks and combustion chambers.
3. Ingredients and performance
Role of alloying elements:
The main function of chromium in nickel-based deformable high-temperature alloys is to increase oxidation resistance and corrosion resistance.
The main function of chromium in nickel-based deformable high-temperature alloys is to increase oxidation resistance and corrosion resistance.
The chromium content of nickel-based deformable high-temperature alloys developed in the 1940s and 1950s was as high as 18% to 20%. In the 1960s, in order to improve the high-temperature strength, the chromium content was reduced to 8% to 12%. Excessive chromium reduction will damage the oxidation resistance and corrosion resistance.
More tungsten, molybdenum, cobalt and other elements are added to the solid solution strengthened nickel-based deformable high-temperature alloy.
Weakly age-hardened nickel-based deformed high-temperature alloys can be added with a certain amount of age-hardening elements such as aluminum, titanium, and niobium.
Large amounts of aluminum, titanium, and niobium can be added to the intensively aging-strengthened nickel-based deformable high-temperature alloy, but the total amount cannot exceed 7.5%. Grain boundary strengthening elements such as boron, cerium, and magnesium are also added.
Organizational characteristics:
The main strengthening phase is γ'(Ni₃Al) phase, with a content of about 20% to 55%.
Another type of strengthening phase is the y" (Ni₃Nb) phase, which contributes much more to the strength below 700°C than the y' phase, and significantly improves the yield strength. It is a well-known strengthening phase in turbine disk materials.
The main strengthening phase is γ'(Ni₃Al) phase, with a content of about 20% to 55%.
Another type of strengthening phase is the y" (Ni₃Nb) phase, which contributes much more to the strength below 700°C than the y' phase, and significantly improves the yield strength. It is a well-known strengthening phase in turbine disk materials.
Processing method: Deformed high-temperature alloys have low plasticity and high deformation resistance, especially strong aging-strengthening nickel-based deformed high-temperature alloys with high Y' phase. It is difficult to deform them using ordinary hot working methods, and some special processing techniques are often required, such as direct rolling of ingots, direct rolling of ingots with jackets, and jacketed upsetting. Magnesium microalloying and bending grain boundary heat treatment processes are also used to improve plasticity.
Nickel-based casting high temperature alloy
(cast nickel -base superallo2)
(cast nickel -base superallo2)
Cast high-temperature alloys with nickel as the main component are indicated by "K" plus a serial number, such as K1, K2, etc.
With the increase of operating temperature and strength, the alloying degree of high-temperature alloys becomes higher and higher, hot forming becomes more and more difficult, and casting process must be used for production.
In addition, the complex internal cavity of the hollow blade using cooling technology can only be produced by precision casting process. In this way, the nickel-based deformed high-temperature alloy is transformed into a nickel-based cast high-temperature alloy.
Add elements and their functions:
Nickel-based cast high-temperature alloys use γ phase as the matrix, and add aluminum, titanium, niobium, tantalum, etc. to form γ' phase for strengthening. The amount of γ' phase is relatively large, and some alloys are as high as 60%; adding cobalt can increase the dissolution temperature of the γ' phase and increase the use temperature of the alloy;
Nickel-based cast high-temperature alloys use γ phase as the matrix, and add aluminum, titanium, niobium, tantalum, etc. to form γ' phase for strengthening. The amount of γ' phase is relatively large, and some alloys are as high as 60%; adding cobalt can increase the dissolution temperature of the γ' phase and increase the use temperature of the alloy;
Molybdenum, tungsten and chromium have the function of strengthening solid solution. Chromium, molybdenum and tantalum can also form a series of carbides that strengthen grain boundaries. Aluminum and chromium contribute to oxidation resistance, but chromium reduces the solubility and high-temperature strength of the y' phase, so the chromium content should be lower. Hafnium: improves the medium-temperature plasticity and strength of the alloy. In order to strengthen the grain boundaries, appropriate amounts of boron, zirconium and other elements are added.
Disadvantages and ways to overcome them
(1) Slightly poor fatigue performance, low plasticity, and decreased organizational stability during use;
(1) Slightly poor fatigue performance, low plasticity, and decreased organizational stability during use;
(2) There is looseness and the performance fluctuates greatly.
In order to alleviate these shortcomings, a high-boron, low-carbon nickel-based casting high-temperature alloy was first developed in the United States in 1968. While other elements in the nickel-based casting high-temperature alloy remain unchanged, the boron content is increased by 10 to 20 times and the carbon content is reduced to
0.01% to 0.03%, which improves the strength and plasticity of the alloy, reduces porosity, and improves the long-term stability of the organization. This type of alloy has been put into practical use in the United States.
In order to alleviate these shortcomings, a high-boron, low-carbon nickel-based casting high-temperature alloy was first developed in the United States in 1968. While other elements in the nickel-based casting high-temperature alloy remain unchanged, the boron content is increased by 10 to 20 times and the carbon content is reduced to
0.01% to 0.03%, which improves the strength and plasticity of the alloy, reduces porosity, and improves the long-term stability of the organization. This type of alloy has been put into practical use in the United States.
Application
Nickel-based cast high-temperature alloys are used for the most critical high-temperature components of gas turbines for aircraft, ships, industry, vehicles and the oil and gas industry, such as turbine blades, guide vanes and integral turbines.
Nickel-based cast high-temperature alloys are used for the most critical high-temperature components of gas turbines for aircraft, ships, industry, vehicles and the oil and gas industry, such as turbine blades, guide vanes and integral turbines.
4. Production process
In terms of smelting: in order to obtain purer molten steel and reduce the gas content and harmful element content; at the same time, due to the presence of easily oxidized elements such as Al, Ti in some alloys, non-vacuum smelting is difficult to control; in order to obtain better thermoplasticity, nickel-based heat-resistant alloys are usually smelted in a vacuum induction furnace, or even produced by vacuum induction smelting plus vacuum consumable furnace or electric slag furnace remelting.
In terms of smelting: in order to obtain purer molten steel and reduce the gas content and harmful element content; at the same time, due to the presence of easily oxidized elements such as Al, Ti in some alloys, non-vacuum smelting is difficult to control; in order to obtain better thermoplasticity, nickel-based heat-resistant alloys are usually smelted in a vacuum induction furnace, or even produced by vacuum induction smelting plus vacuum consumable furnace or electric slag furnace remelting.
Deformation
Forging and rolling processes are used. For alloys with poor thermoplasticity, rolling after extrusion or direct extrusion with soft steel (or stainless steel) sheathing is even used. The purpose of deformation is to break up the casting structure and optimize the microstructure.
Forging and rolling processes are used. For alloys with poor thermoplasticity, rolling after extrusion or direct extrusion with soft steel (or stainless steel) sheathing is even used. The purpose of deformation is to break up the casting structure and optimize the microstructure.
Casting
Casting: Usually a vacuum induction furnace is used to melt the master alloy to ensure the composition and control the gas and impurity content, and the parts are made by vacuum remelting-precision casting.
Casting: Usually a vacuum induction furnace is used to melt the master alloy to ensure the composition and control the gas and impurity content, and the parts are made by vacuum remelting-precision casting.
Heat treatment
Heat treatment: Deformed alloys and some cast alloys need to be heat treated, including solution treatment, intermediate treatment and aging treatment. Taking Udmet 500 alloy as an example, its heat treatment system is divided into four stages: 1. Solution treatment
aging treatment, 1175℃, 2 hours, air cooling;
Heat treatment: Deformed alloys and some cast alloys need to be heat treated, including solution treatment, intermediate treatment and aging treatment. Taking Udmet 500 alloy as an example, its heat treatment system is divided into four stages: 1. Solution treatment
aging treatment, 1175℃, 2 hours, air cooling;
2. Intermediate treatment, 1080℃, 4 hours, air cooling;
3. Primary aging treatment, 843℃, 24 hours, air cooling;
4. Secondary aging treatment, 760℃, 16 hours, air cooling.
To obtain the required organizational state and good comprehensive performance.
Application and development trend of 718 nickel-based high-temperature alloy
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