K 17 what is a superalloy?

According to the existing theory, 760℃ high temperature materials can be mainly divided into superalloy, nickel-based superalloy and cobalt-based superalloy according to matrix elements. According to the preparation process, it can be divided into deformed superalloys, cast superalloys and powder metallurgy superalloys. 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.

Development of 760℃ High Temperature Materials 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, Britain first added a small amount of aluminum and titanium to 80Ni-20Cr alloy to form γ element for strengthening, and developed the first high-temperature strength nickel-based alloy. 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. Adding elements such as nickel and tungsten into cobalt-based alloys, a variety of high-temperature alloys have been developed, 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 directional crystal 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.

760℃ high temperature material deformation superalloy

Deformed superalloy refers to an alloy that can be hot and cold deformed. The working temperature range is -253 ~ 1320℃, and it has good mechanical properties, comprehensive strength and toughness indexes, and high oxidation resistance 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, solution strengthened iron-based alloy 2, age hardened iron-based alloy 3, solution strengthened nickel-based alloy 4 and cobalt-based alloy. After GH, the second, third and fourth digits indicate the serial number.

1, solid solution strengthened alloy

The service temperature range is 900 ~ 1300℃, and the highest oxidation resistance temperature is 1320℃. For example, alloy GH 128 has a tensile strength of 850MPa at room temperature and a yield strength of 350MPa. 1000℃ tensile strength is 140MPa and elongation is 85%. Under 1000℃ and 30MPa stress, the durable life is 200 hours and the elongation is 40%. Solid solution alloys are usually used to manufacture combustion chambers and casings of aviation and aerospace engines.

2. Aging strengthening alloy

The service temperature is -253 ~ 950℃, which is generally used to manufacture turbine disks and blades of aviation and aerospace engines. The working temperature of alloy used to manufacture turbine disk is -253 ~ 700℃, which requires good high and low temperature strength and fatigue resistance. For example, the highest yield strength of alloy GH4 169 at 650℃ is1000 MPa; ; The alloy temperature of the blade can reach 950℃, such as GH220 alloy, the tensile strength at 950℃ is 490MPa, and the durability at 940℃ and 200 MPa is more than 40 hours.

Deformed superalloys mainly provide structural forgings, cakes, rings, bars, plates, tubes, belts and wires for aerospace, aviation, nuclear energy and petroleum civil industries. [ 1]

Casting superalloy with 800 MPa grade high temperature material at 760℃

Cast superalloy refers to a kind of superalloy that can or can only be used for casting formed parts. Its main features are:

1. It has a wider range of components. Because it is unnecessary to consider its deformability, the design of the alloy can focus on optimizing its performance. For example, for nickel-based superalloys, the γ' content can reach 60% or higher by adjusting the composition, so that the alloy can still maintain excellent properties 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 casting method, superalloy castings with any complex structure and shape with near net shape or no allowance can be designed and manufactured according to the needs of parts.

According to the service temperature of cast alloys, they can be divided into the following three categories:

The first category: used for equiaxed casting superalloys at -253 ~ 650℃. These alloys have good comprehensive properties in a wide temperature range, especially at low temperature, and can keep their strength and plasticity unchanged. For example, K4 169 alloy, which is widely used in aviation and aerospace engines, has a tensile strength of 1000MPa, a yield strength of 850MPa and a tensile plasticity of 15% at 650℃. The durable life under 650℃ and 620MPa stress is 200 hours. It has been used to manufacture diffuser housings in aero-engines and complex structural parts of various pumps in aero-engines.

The second category: used for equiaxed casting superalloys at 650 ~ 950℃. These alloys have high mechanical properties and thermal corrosion resistance at high temperature. For example, K4 19 alloy has a tensile strength of more than 700MPa and a tensile plasticity of more than 6% at 950℃. The ultimate strength at 950℃ for 200 hours is greater than 230MPa. This alloy is suitable for aero-engine turbine blades, guide blades and integral casting turbines.

The third category: directionally solidified columnar crystals and single crystal superalloys used at 950 ~ 1 100℃ have excellent comprehensive properties, oxidation resistance and hot corrosion resistance in this temperature range. For example, the single crystal alloy DD402 has a durable life of more than 100 hours under the stress of100℃ and 130MPa. This is the highest temperature turbine blade material used in China, which is suitable for manufacturing the first stage turbine blade of new high performance engine.

With the continuous improvement of precision casting technology, new special processes are constantly emerging. Fine-grained casting technology, directional solidification technology and CA technology for complex thin-walled structures have greatly improved the level of casting superalloys and continuously improved their application scope.

760℃800MPa high temperature material powder metallurgy superalloy

High-temperature alloy powder products are made of high-temperature alloy powder by atomization, hot isostatic pressing or forging after hot isostatic pressing. Using powder metallurgy technology, the powder particles are fine, the cooling speed is fast, so the composition is uniform, there is no macro segregation, and the grain is 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 are greatly improved.

FGH95 powder metallurgy superalloy with tensile strength of 1500MPa; At 650℃; The durable life under the stress of 1034MPa is more than 50 hours, and it is a disc-shaped powder metallurgy superalloy with the highest strength grade at 650℃. Powder metallurgy superalloy can meet the application requirements of high stress level engine, and is the first choice material for high temperature components such as turbine disk, compressor disk and turbine baffle of high thrust-weight ratio engine.

1200℃ 100MPa high temperature material oxide dispersion strengthened alloy

It is a special high-temperature alloy formed by a unique mechanical alloying (MA) process. Ultra-stable ultrafine (less than 50nm) oxide dispersion strengthening phase is uniformly dispersed in the alloy matrix at high temperature. Its alloy strength can still be maintained under the condition close to the melting point of the alloy itself, and it has excellent high-temperature creep performance, excellent high-temperature oxidation resistance and carbon-sulfur corrosion resistance.

At present, there are three kinds of ODS alloys that have been commercialized:

The service temperature of MA956 alloy in oxidizing atmosphere can reach 1350℃, which ranks first in oxidation resistance, carbon and sulfur corrosion resistance of superalloy. Can be use for lining of a combustion cham of an aero-engine.

The service temperature of MA754 alloy in oxidizing atmosphere can reach 1250℃, and it maintains a fairly high high temperature strength and is resistant to alkali glass corrosion. Now it has been used to manufacture labyrinth rings and guide blades of aero-engine guides.

The tensile strength of MA6000 alloy is 222MPa, and the yield strength is192 MPa. At 165438℃. 1 100℃, 1000 hours, and the endurance strength 127MPa, which ranks first among superalloys, can be used for aero-engine blades.

Intermetallic compound high temperature material

Intermetallic compound high temperature materials are a kind of light high temperature materials with important application prospects. In recent ten years, the basic research, alloy design, technological process development and application research of intermetallic compounds have matured, especially in the preparation and processing technology, toughening and strengthening, mechanical properties and application research of Ti-Al, Ni-Al and Fe-Al systems.

Ti3Al-based alloy (TAC- 1), TiAl-based alloy (TAC-2) and Ti2AlNb-based alloy have the advantages of low density (3.8 ~ 5.8g/cm3), high high high temperature strength, high hardness, excellent oxidation resistance and creep resistance, which 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 a good application prospect. Fe3Al-based alloy has good oxidation resistance and wear resistance, high strength at medium temperature (below 600℃) and low cost, so it is a new material that can partially replace stainless steel.

Environmental superalloys

In many fields of civil industry, in-service component materials are in high temperature and corrosive environment. In order to meet the market demand, superalloys are classified according to the use environment of materials.

1, super alloys master alloy series.

2. Corrosion-resistant superalloy plates, bars, wires, belts, tubes and forgings.

3. High-strength and corrosion-resistant superalloy bars, spring wires, welding wires, plates, strips and forgings.

4, glass corrosion-resistant products

5, environmental corrosion resistance, hard surface wear-resistant superalloy series

6. Special precision castings (blades, supercharged turbines, turbine rotors, conduits, instrument joints)

7. Centrifuges, high-temperature shafts and accessories for glass wool production. Cobalt-based alloy heat-resistant pad and slide rail for billet heating furnace.

9. Valve seat ring

10, casting U-shaped resistance band.

1 1, centrifugal cast pipe series

12, nano-material series products

13, light specific gravity high temperature structural material

14, functional materials (expansion alloy, high temperature and high elasticity alloy, constant elasticity alloy series)

15, biomedical materials series products

16, electronic engineering target series products

17, power plant nozzle series products

18, stellite wear-resistant sheet

19, ultra-high temperature anti-oxidation corrosion furnace roller, radiation tube.