Knowledge of high temperature alloy steel
Knowledge of high temperature alloy steel
High temperature alloy steel is a type of alloy used in high temperature and severe mechanical stress and oxidation and corrosion environment. With the development of science and technology, superalloys have gradually formed six relatively complete parts.
1. Deformed high temperature alloy steel
Deformed high-temperature alloy steel refers to a type of alloy that can be processed by hot and cold deformation, working temperature range -253～1320℃, has good mechanical properties and 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.
(1) Solid solution strengthened alloy steel
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 steel
The operating 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.
Deformed superalloys mainly provide structural forgings, cakes, rings, bars, plates, pipes, strips and wires for the aerospace, aviation, nuclear energy, petroleum and civil industries.
2. Casting high temperature alloy steel
Casting high-temperature alloy steel refers to a type of high-temperature alloy that can or can only use casting methods to form parts. Its main features are:
(1)It has a wider range of composition. 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 content of γ'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 needs of the parts.
According to the service temperature of cast alloy steel, it can be divided into the following three categories:
The first type: equiaxed crystal casting superalloys used at -253～650℃. This type of alloy has 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 ℃. This type of alloy has higher 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 and single crystal superalloys used at 950～1100℃. This kind of alloy has 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 are also emerging. 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.
3. Powder metallurgy high temperature alloy steel
Atomized high-temperature alloy powder, hot isostatic pressing or hot isostatic pressing, and then forging into a production process to produce high-temperature alloy 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℃; the endurance life is more than 50 hours under 1034MPa stress. It is currently a kind of disc powder metallurgy superalloy with the highest level of strength under 650℃ 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.
4. Oxide dispersion strengthening (ODS) alloy steel
It is a special high-temperature alloy formed by a unique mechanical alloying (MA) process, ultra-fine (less than 50nm) ultra-stable oxide dispersion strengthening phase at high temperature 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.
At present, there are mainly three kinds of ODS alloys that have been commercialized:
MA956 alloy can be used at a temperature of 1350℃ in an oxidizing atmosphere, which ranks first among high-temperature alloys in terms of oxidation resistance, carbon and sulfur corrosion resistance. It can be used as a lining in the combustion chamber of aero-engine.
The MA754 alloy can be used in an oxidizing atmosphere at a temperature of up to 1250°C and maintains a fairly high high-temperature strength and is resistant to corrosion by medium-alkali glass. 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.
5. Intermetallic compound high temperature materials
Intermetallic high-temperature materials are a kind of high-temperature materials with important application prospects and light specific gravity that have been researched and developed recently. 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, excellent oxidation resistance, creep resistance, etc. 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.
6, environmental superalloys
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)Centrifuge, high temperature shaft and accessories for glass wool production
(8)Cobalt-based alloy heat-resistant pad and slide rail for billet heating furnace
(9)Valve seat ring
(10) Casting "U"-shaped resistance band
(11) Centrifugal cast pipe series
(12) Nano material series products
(13) Light specific gravity high temperature structural materials
(14)Functional materials (expandable alloy, high temperature and high elastic alloy, constant elastic alloy series)
(15)Biomedical materials 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 corrosion furnace roller and radiant tube.
High temperature alloy steel is a type of alloy used in high temperature and severe mechanical stress and oxidation and corrosion environment. With the development of science and technology, superalloys have gradually formed six relatively complete parts.
1. Deformed high temperature alloy steel
Deformed high-temperature alloy steel refers to a type of alloy that can be processed by hot and cold deformation, working temperature range -253～1320℃, has good mechanical properties and 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.
(1) Solid solution strengthened alloy steel
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 steel
The operating 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.
Deformed superalloys mainly provide structural forgings, cakes, rings, bars, plates, pipes, strips and wires for the aerospace, aviation, nuclear energy, petroleum and civil industries.
2. Casting high temperature alloy steel
Casting high-temperature alloy steel refers to a type of high-temperature alloy that can or can only use casting methods to form parts. Its main features are:
(1)It has a wider range of composition. 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 content of γ'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 needs of the parts.
According to the service temperature of cast alloy steel, it can be divided into the following three categories:
The first type: equiaxed crystal casting superalloys used at -253～650℃. This type of alloy has 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 ℃. This type of alloy has higher 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 and single crystal superalloys used at 950～1100℃. This kind of alloy has 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 are also emerging. 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.
3. Powder metallurgy high temperature alloy steel
Atomized high-temperature alloy powder, hot isostatic pressing or hot isostatic pressing, and then forging into a production process to produce high-temperature alloy 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℃; the endurance life is more than 50 hours under 1034MPa stress. It is currently a kind of disc powder metallurgy superalloy with the highest level of strength under 650℃ 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.
4. Oxide dispersion strengthening (ODS) alloy steel
It is a special high-temperature alloy formed by a unique mechanical alloying (MA) process, ultra-fine (less than 50nm) ultra-stable oxide dispersion strengthening phase at high temperature 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.
At present, there are mainly three kinds of ODS alloys that have been commercialized:
MA956 alloy can be used at a temperature of 1350℃ in an oxidizing atmosphere, which ranks first among high-temperature alloys in terms of oxidation resistance, carbon and sulfur corrosion resistance. It can be used as a lining in the combustion chamber of aero-engine.
The MA754 alloy can be used in an oxidizing atmosphere at a temperature of up to 1250°C and maintains a fairly high high-temperature strength and is resistant to corrosion by medium-alkali glass. 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.
5. Intermetallic compound high temperature materials
Intermetallic high-temperature materials are a kind of high-temperature materials with important application prospects and light specific gravity that have been researched and developed recently. 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, excellent oxidation resistance, creep resistance, etc. 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.
6, environmental superalloys
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)Centrifuge, high temperature shaft and accessories for glass wool production
(8)Cobalt-based alloy heat-resistant pad and slide rail for billet heating furnace
(9)Valve seat ring
(10) Casting "U"-shaped resistance band
(11) Centrifugal cast pipe series
(12) Nano material series products
(13) Light specific gravity high temperature structural materials
(14)Functional materials (expandable alloy, high temperature and high elastic alloy, constant elastic alloy series)
(15)Biomedical materials 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 corrosion furnace roller and radiant tube.
