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.
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.
Second, casting superalloys.
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 their application scope has been continuously improved.
Three. 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.
Four. 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. It has been used to manufacture guide rings and guide vanes of aero-engines.
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 high-temperature alloys, can be used for aero-engine blades.
Five, intermetallic compound high temperature materials
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 rigidity, 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.