What are the high-temperature alloy materials included?

What is the material of high temperature alloy, and what are the main materials of high temperature alloy?

High-temperature alloys are a class of alloys used in high-temperature harsh mechanical stress and oxidation and corrosion environments. With the development of science and technology, high temperature alloy gradually formed six more complete parts.

 

　　1. deformed superalloy

Deformed superalloy refers to a kind of alloy that can be processed by hot and cold deformation, the working temperature range is -253~1320 ℃, has good mechanical properties and comprehensive strength and toughness indicators, and has 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 strengthening alloy

The use of temperature range of 900~1300 ℃,.. oxidation temperature up to 1320 ℃. For example, GH128 alloy has a room temperature tensile strength of 850MPa and a yield strength of 350MPa. The tensile strength at 1000 ℃ is 140MPa, the elongation is 85%, the lasting life at 1000 ℃ and 30MPa stress is 200 hours, and the elongation is 40%. Solid solution alloy is generally used for the production of aviation, aerospace engine combustion chamber, casing and other components.

2. Aging strengthened alloy

The use temperature is -253~950 ℃, generally used for the production of aviation, aerospace engine turbine disk and blades and other structural parts. The working temperature of the alloy for making turbine disks is -253~700 ℃, which requires good high and low temperature strength and fatigue resistance. For example: GH4169 alloy, at 650 ℃ .. the yield strength of 1000MPa; The alloy temperature for making blades can reach 950 ℃, for example: GH220 alloy, the tensile strength at 950 ℃ is 490MPa, and the lasting life at 940 ℃ and 200MPa is more than 40 hours.

Deformed high-temperature alloys mainly provide structural forgings, cakes, rings, bars, plates, pipes, strips and wires for aerospace, aviation, nuclear energy and petroleum civil industries.

 

　2. cast superalloy

Cast superalloys are a class of superalloys that can or can only be cast to form parts. Its main features are:

1. With a wider composition range, since it is not necessary to take into account its deformation processing performance, the design of the alloy can focus on optimizing its performance. For example, for nickel-based high-temperature alloys, the composition can be adjusted to make the γ' content reach 60% or higher, so that the alloy can still maintain excellent properties at temperatures up to 85% of the melting point of the alloy.

Due to the special advantages of the casting method, it can design and manufacture high-temperature alloy castings with any complex structure and shape with near net shape or no allowance according to the use needs of the parts.

According to the use temperature of the cast alloy, it can be divided into the following three categories:

The first category: equiaxed crystal casting high temperature alloys used in -253~650 ℃. These alloys have good comprehensive properties in a large range of temperatures, especially at low temperatures to maintain strength and plasticity are not reduced. For example, K4169 alloy, which is used in a large amount 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 at 650 ℃ and 620MPa stress is 200 hours. It has been used to make diffuser cases in aero engines and complex structural parts for various pumps in aerospace engines.

The second category: equiaxed crystal casting high-temperature alloys used at 650~950 ℃. These alloys have high mechanical properties and hot corrosion resistance at high temperatures. For example, K419 alloy has a tensile strength of more than 700MPa and a tensile plasticity of more than 6% at 950 ℃. At 950 ℃, the endurance strength limit for 200 hours is greater than 230MPa. These alloys are suitable for use as aero-engine turbine blades, guide vanes and integral casting turbines.

The third category: directional solidification column crystal and single crystal high temperature alloy used in 950~1100 ℃. This kind of alloy has excellent comprehensive performance, oxidation resistance and hot corrosion resistance in this temperature range. For example, DD402 single crystal alloy has a durable life of more than 100 hours under the stress of 1100 ℃ and 130MPa. This is the turbine blade material of the domestic use temperature, which is suitable for making the first-stage turbine blades of the new high-performance engine.

With the continuous improvement of precision casting technology, new special processes are also emerging. Fine grain casting technology, directional solidification technology and CA technology of complex thin-walled structural parts have greatly improved the level of casting high-temperature alloys, and the scope of application has been continuously improved.

 

　　3. powder metallurgy superalloy

The use of atomized high-temperature alloy powder, by hot isostatic pressing molding or hot isostatic pressing and then by forging molding production process to produce high-temperature alloy powder products. The powder metallurgy process, because the powder particles are small, the cooling speed is fast, and the composition is uniform, no macro segregation, and the grain is small, the hot workability is good, the metal utilization rate is high, the cost is low, especially the yield strength and fatigue performance of the alloy are greatly improved.

FGH95 powder metallurgy superalloy, 650 ℃ tensile strength 1500MPa; The durable life under 1034MPa stress is greater than 50 hours. It is a disc powder metallurgy superalloy with current strength level under 650 ℃ working conditions. Powder metallurgy superalloys can meet the requirements of engines with high stress levels, and are the material of choice for high-temperature components such as turbine discs, compressor discs and turbine baffles of engines with high thrust-to-weight ratios.

 

　　4. oxide dispersion strengthened (ODS) alloys

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

At present, there are three main ODS alloys that have been commercially produced:

The use temperature of MA956 alloy in oxidizing atmosphere can reach 1350 ℃, which ranks first in oxidation resistance, carbon and sulfur corrosion resistance of high temperature alloy. Can be used for aircraft engine combustion chamber lining.

MA754 alloy in oxidizing atmosphere temperature up to 1250 ℃ and maintain high temperature strength, alkali glass corrosion resistance. It has been used in the production of aero-engine guide ratchet rings and guide vanes.

MA6000 alloy has a tensile strength of 222MPa and a yield strength of 192MPa at 1100 ℃. At 1100 ℃, the 1000-hour lasting strength is 127MPa, ranking first among high-temperature alloys and can be used for aero-engine blades.

 

　　5. intermetallic compound high temperature materials

Intermetallic high-temperature materials are a class of light-weight high-temperature materials with important application prospects. For more than ten years, the basic research, alloy design, process development and application research of intermetallic compounds have been mature, especially in the preparation and processing technology, toughening and strengthening, mechanical properties and application research of Ti-Al, Ni-Al and Fe-Al materials.

Ti3Al-based alloy (TAC-1),TiAl-based alloy (TAC-2) and Ti2AlNb-based alloy with low density (3.8~5.8g/cm3), high temperature high strength, high rigidity and excellent oxidation resistance, creep resistance and other advantages, can make the structural parts weight loss of 35 ~ 50%. Ni3Al-based alloy, MX-246 has good corrosion resistance, wear resistance and cavitation corrosion resistance, showing excellent application prospects. Fe3Al-based alloy has good oxidation resistance, wear resistance and corrosion resistance, high strength at medium temperature (less than 600 ℃), and low cost. It is a new material that can partially replace stainless steel.

 

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