High temperature alloys are divided into three types of materials: 760℃ high temperature materials, 1200℃ high temperature materials and 1500℃ high temperature materials, with a tensile strength of 800MPa. In other words, it refers to high-temperature metal materials that work for a long time under 760-1500℃ and certain stress conditions. They have excellent high-temperature strength, good oxidation and thermal corrosion resistance, good fatigue performance, fracture toughness and other comprehensive properties. It has become an irreplaceable key material for the hot end components of military and civilian gas turbine engines.
According to the existing theory, 760℃ high-temperature materials can be divided into iron-based superalloys, nickel-based superalloys and cobalt-based superalloys according to the matrix elements. According to the preparation process, it can be divided into deformed superalloys, casting superalloys and powder metallurgy superalloys. According to the strengthening method, there are solid solution strengthening type, precipitation strengthening type, oxide dispersion strengthening type and fiber strengthening type. Superalloys are mainly used to manufacture high-temperature components such as turbine blades, guide blades, turbine disks, high-pressure compressor disks and combustion chambers of aviation, naval and industrial gas turbines, and are also used to manufacture aerospace vehicles, rocket engines, nuclear reactors, petrochemical equipment, and Energy conversion devices such as coal conversion.
Category
760℃ high temperature material deformed superalloy
Wrought superalloy refers to a type of alloy that can be processed by hot and cold deformation, has a working temperature range of -253 to 1320°C, has good mechanical properties, comprehensive strength and toughness indicators, and has high oxidation and corrosion resistance. According to its heat treatment process, it can be divided into solid solution strengthening alloy and aging strengthening alloy. The first digit after GH indicates the classification number, namely 1, solid solution strengthened iron-based alloy 2, age-hardening iron-based alloy 3, solid solution strengthened nickel-based alloy 4, cobalt-based alloy GH, two, three, and four digits The number indicates the sequence number.
1. Solid solution strengthened alloy
The operating temperature range is 900～1300℃, and the highest anti-oxidation temperature is 1320℃. For example, GH128 alloy has a room temperature tensile strength of 850MPa and a yield strength of 350MPa; a tensile strength of 140MPa at 1000°C, an elongation of 85%, a durability life of 200 hours at a stress of 1000°C and 30MPa, and an elongation of 40%. Solid solution alloys are generally used to make components such as combustion chambers and casings of aviation and aerospace engines.
2. Aging strengthened alloy
The service temperature is -253～950℃, and it is generally used to make structural parts such as turbine discs and blades of aviation and aerospace engines. The working temperature of the alloy used to make the turbine disk is -253～700℃, which requires good high and low temperature strength and fatigue resistance. For example: GH4169 alloy, the highest yield strength at 650℃ is 1000MPa; the alloy temperature for making blades can reach 950℃, for example: GH220 alloy, the tensile strength at 950℃ is 490MPa, the endurance life of 940℃, 200MPa is more than 40 hours.
Wrought superalloys mainly provide structural forgings, cakes, rings, bars, plates, pipes, strips and wires for aerospace, aviation, nuclear energy, and petroleum and civil industries.
760℃800MPa grade high temperature material casting superalloy
Casting high-temperature alloys refers to a type of high-temperature alloys that can or can only be molded parts by casting methods. Its main features are:
1. It has a wider range of compositions. Since it is not necessary to take into account its deformation processing performance, the design of the alloy can focus on optimizing its use performance. For example, for nickel-based superalloys, the γ'content can be adjusted to 60% or higher by adjusting the composition, so that the alloy can still maintain excellent performance at a temperature as high as 85% of the melting point of the alloy.
2. It has a wider application field. Due to the special advantages of the casting method, it is possible to design and manufacture near-net-shape or no margin superalloy castings with arbitrary complex structures and shapes according to the use needs of the parts.
According to the service temperature of the casting alloy, it can be divided into the following three categories:
The first category: equiaxed crystal casting superalloys used at -253～650℃ have good comprehensive properties in a wide range of temperatures, especially at low temperatures that can maintain strength and plasticity without decreasing. For example, the K4169 alloy, which is used in aerospace and aerospace engines, has a tensile strength of 1000 MPa, a yield strength of 850 MPa, and a tensile plasticity of 15% at 650°C; its endurance life under stress of 650°C and 620 MPa is 200 hours. It has been used in the manufacture of diffuser casings in aero-engines and various complex structural parts for pumps in aerospace engines.
The second category: Equiaxed crystal casting superalloys used at 650-950°C have high mechanical properties and thermal corrosion resistance at high temperatures. For example, K419 alloy, at 950°C, the tensile strength is greater than 700MPa, and the tensile ductility is greater than 6%; at 950°C, the endurance strength limit for 200 hours is greater than 230MPa. This type of alloy is suitable for use as aero-engine turbine blades, guide vanes and cast turbines.
The third category: Directionally solidified columnar crystals and single crystal superalloys used at 950 to 1100°C have excellent comprehensive performance, oxidation resistance and thermal corrosion resistance in this temperature range. For example, DD402 single crystal alloy has a durability life of more than 100 hours under a stress of 1100°C and 130MPa. This is the highest temperature turbine blade material used in China, and it is suitable for making the first-stage turbine blades of new high-performance engines.
With the continuous improvement of precision casting technology, new special processes continue to appear. Fine-grain casting technology, directional solidification technology, CA technology of complex thin-walled structural parts, etc. have greatly improved the level of casting high-temperature alloys, and the scope of application has continued to increase.
760℃800MPa grade high temperature material powder metallurgy superalloy
A production process of atomized superalloy powder, hot isostatic pressing or hot isostatic pressing, and then forging is used to manufacture superalloy powder products. Adopting powder metallurgy technology, due to the fine powder particles and fast cooling rate, the composition is uniform, there is no macro segregation, and the crystal grains are fine, the hot workability is good, the metal utilization rate is high, and the cost is low, especially the yield strength and fatigue performance of the alloy. Great improvement.
FGH95 powder metallurgy superalloy has a tensile strength of 1500MPa at 650°C; the endurance life is more than 50 hours under a stress of 1034MPa, and it is currently a kind of disc powder metallurgy superalloy with the highest level of strength under 650°C working conditions. Powder metallurgy superalloys can meet the requirements of engines with higher stress levels, and are the materials of choice for high-temperature components such as turbine discs, compressor discs, and turbine baffles for engines with high thrust-to-weight ratio.
1200℃100MPa grade high temperature material oxide dispersion strengthening (ODS) alloy
It is a special high-temperature alloy formed by using a unique mechanical alloying (MA) process, and ultra-fine (less than 50nm) super-stable oxide dispersion strengthening phase at high temperature is uniformly dispersed in the alloy matrix. The strength of the alloy can be maintained close to the melting point of the alloy itself, and it has excellent high-temperature creep performance, superior high-temperature oxidation resistance, and carbon and sulfur corrosion resistance.
There are currently three main types of ODS alloys that have been commercially produced:
The MA956 alloy can be used at a temperature of 1350°C in an oxidizing atmosphere, ranking first among high-temperature alloys in terms of oxidation resistance, carbon and sulfur corrosion resistance. It can be used to line the combustion chamber of aero-engine.
The MA754 alloy can be used in an oxidizing atmosphere at a temperature of 1250°C and maintains a fairly high high-temperature strength and is resistant to alkali glass corrosion. It has been used to make aero-engine guide grate ring and guide vane.
MA6000 alloy has a tensile strength of 222MPa at 1100°C and a yield strength of 192MPa; at 1100°C, the 1000-hour endurance strength is 127MPa, ranking first among superalloys and can be used for aero engine blades.
High temperature intermetallic compound material
Intermetallic high-temperature materials are a type of high-temperature materials with important application prospects and light specific gravity that have been recently researched and developed. For more than ten years, basic research on intermetallic compounds, alloy design, process development and application research have been mature, especially in the preparation and processing technology, toughening and strengthening of Ti-Al, Ni-Al and Fe-Al materials , Mechanical properties and application research have made remarkable achievements.
Ti3Al-based alloys (TAC-1), TiAl-based alloys (TAC-2) and Ti2AlNb-based alloys have low density (3.8～5.8g/cm3), high temperature, high strength, high stiffness, and excellent oxidation and creep resistance. Advantages, it can reduce the weight of structural parts by 35-50%. Ni3Al-based alloy, MX-246 has good corrosion resistance, wear resistance and cavitation resistance, showing an excellent application prospect. Fe3Al-based alloy has good oxidation resistance and corrosion resistance, high strength at medium temperature (less than 600°C), and low cost. It is a new material that can partially replace stainless steel.
Environmental superalloy
In many areas of the civil industry, the component materials in service are in a high-temperature corrosive environment. In order to meet the needs of the market, a series of superalloys are classified according to the use environment of the material.
1. High temperature alloy master alloy series
2. Corrosion-resistant high-temperature alloy plates, rods, wires, belts, tubes and forgings
3. High-strength, corrosion-resistant high-temperature alloy bars, spring wires, welding wires, plates, strips, and forgings
4. Glass corrosion-resistant series products
5、Environmental corrosion resistance, hard surface wear-resistant high-temperature alloy series
6. Special precision casting parts (blades, supercharged turbines, turbine rotors, guides, instrument joints)
7. Centrifuges, high-temperature shafts and accessories for glass wool production 8. Cobalt-based alloy heat-resistant pads and slide rails for billet heating furnaces
9. Valve seat ring
10. Casting "U"-shaped resistance band
11. Centrifugal cast pipe series
12. Nano-material series products
13. Light-weight and high-temperature structural materials
14. Functional materials (expandable alloy, high temperature and high elastic alloy, constant elastic alloy series)
15. Biomedical material series products
16. Target products for electronic engineering
17. Power plant nozzle series products
18. Stellite alloy wear-resistant sheet
19. Ultra-high temperature anti-oxidation and corrosion-resistant furnace rolls and radiant tubes.
development trend
The development trend of superalloys is to further increase the working temperature of the alloys and to improve the ability to withstand various loads at medium or high temperatures, and to extend the life of the alloys. As far as turbine blade materials are concerned, single crystal blades will enter the practical stage, and the overall performance of directional crystal blades will be improved.
In addition, it is possible to use chilled alloy powder to manufacture multi-layer diffusion-connected hollow blades to meet the needs of increasing the gas temperature. As far as the guide vane and combustion chamber materials are concerned, it is possible to use oxide dispersion-strengthened alloys to greatly increase the operating temperature. In order to improve corrosion resistance and abrasion resistance, alloy protective coating materials and processes will also be further developed.
