What is the material of high temperature alloy?
High-temperature alloys are a class of metal materials based on iron, nickel and cobalt, which can work for a long time at high temperatures above 600℃ and under certain stress. Aerospace field and energy field.
High-temperature alloys are iron, nickel, cobalt-based, can work at high temperatures above 600 ℃ and under certain stresses for a long time a class of metal materials; and has a high temperature strength, good resistance to oxidation and corrosion resistance, good fatigue properties, fracture toughness and other comprehensive properties. High-temperature alloys are single austenite organization, with good organizational stability and reliability in various temperatures.
Based on the above performance characteristics, and high-temperature alloys are also known as "superalloys", which are widely used in aviation, aerospace, petroleum, chemical, naval, an important material. According to the base element, high temperature alloys are divided into iron-based, nickel-based, cobalt-based high temperature alloys. Iron-based high-temperature alloys can generally only be used at temperatures of 750 to 780°C. For heat-resistant parts used at higher temperatures, nickel-based and refractory metal-based alloys are used. Nickel-based high-temperature alloys occupy a special and important position in the entire field of high-temperature alloys, which are widely used to manufacture the hottest end parts of aviation jet engines and various industrial gas turbines.
Main classification
The traditional classification of high-temperature alloy materials can be done in the following three ways: by matrix element type, alloy strengthening type, and material forming method.
1、By type of matrix element
(1) Iron-based high-temperature alloys
Iron-based high-temperature alloy can also be called heat-resistant alloy steel. Its matrix is Fe element, adding a small amount of Ni, Cr and other alloying elements, heat-resistant alloy steel can be divided into martensite, austenite, pearlite, ferrite heat-resistant steel, etc. according to its normalization requirements.
(2) Nickel-based high-temperature alloys
Nickel-based high-temperature alloys contain more than half of nickel and are suitable for working conditions above 1,000°C. The use of solid solution and aging processes can result in a significant increase in creep resistance and compressive and yield strength. With regard to the analysis of high-temperature alloys used in high-temperature environments, the use of nickel-based high-temperature alloys far exceeds the range of iron-based and cobalt-based high-temperature alloys useful. At the same time, nickel-based high-temperature alloy is also China's largest production, the use of the largest amount of a high-temperature alloy. Many turbine engines turbine blades and combustion chambers, and even turbochargers also use nickel-based alloys as preparation materials. For more than half a century, the high-temperature materials used in aero-engines to withstand high temperatures from the late 1940s 750 ℃ to the late 1990s 1 200 ℃ should be said that this huge increase also prompted the rapid development of casting process processing and surface coating.
(3) Cobalt-based high-temperature alloys
Cobalt-based high-temperature alloy is based on cobalt, with cobalt content accounting for about 60%, while Cr, Ni and other elements need to be added to enhance the heat resistance of high-temperature alloys. Although this high-temperature alloy has better heat resistance, it is not used much because the production of cobalt resources in various countries is relatively small and processing is difficult. Usually used in high temperature conditions ( 600 ~ 1 000 ℃ ) and a longer period of time subject to extreme complex stress high temperature parts, such as the working blades of aircraft engines, turbine discs, combustion chamber hot end components and aerospace engines. In order to obtain better heat resistance, the general conditions to add elements such as W, MO, Ti, Al, Co in the preparation, to ensure its superior thermal fatigue resistance.
2、Alloy strengthening type
According to the type of alloy strengthening, high-temperature alloys can be divided into solid-solution strengthened high-temperature alloys and aging precipitation strengthened alloys.
(1) Solid solution strengthening type
The so-called solid solution strengthening type is to add some alloying elements to the iron, nickel or cobalt-based high-temperature alloy, the formation of single-phase austenite organization, solute atoms make the solid solution matrix dot matrix distortion, so that the solid solution in the slip resistance increases and strengthen. Some solute atoms can reduce the laminar dislocation energy of the alloy system and increase the tendency of dislocation decomposition, resulting in difficult cross-slip migration, and the alloy is strengthened to achieve the purpose of high temperature alloy strengthening.
(2) Aging precipitation strengthening
The so-called aging precipitation strengthening is a heat treatment process in which the alloy workpiece is solid solution treated, cold plastic deformation, and then placed at a higher temperature or room temperature to maintain its performance. For example: GH4169 alloy, the highest yield strength of 1 000 MPa at 650 ℃, the production of blades of the alloy temperature up to 950 ℃.
3、Material forming method
Through the material forming method is divided into: casting high temperature alloy (including ordinary casting alloy, single crystal alloy, directional alloy, etc.), deformation high temperature alloy, powder metallurgy high temperature alloy (including ordinary powder metallurgy and oxide dispersion strengthening high temperature alloy).
(1) Casting high-temperature alloys
Casting method directly prepared parts of the alloy material is called casting high temperature alloy. According to the alloy matrix composition, can be divided into iron-based casting high-temperature alloy, nickel-based casting high-temperature alloy and cobalt-based casting high-temperature alloy 3 types. According to the crystallization method, can be divided into polycrystalline casting high-temperature alloy, directional solidification casting high-temperature alloy, directional eutectic casting high-temperature alloy and single crystal casting high-temperature alloy and other four types.
(2) Deformed high temperature alloys
It is still the most used material in aero-engines and is widely used both at home and abroad, and the annual production of deformed high-temperature alloys in China is about 1/8 of that in the United States [2]. Take GH4169 alloy as an example, it is one of the main varieties with the largest range of applications at home and abroad. China is mainly in the turbine shaft engine bolts, compressors and wheels, oil dump discs as the main parts, with the increasing maturity of other alloy products, the use of deformed high-temperature alloys may gradually reduce, but in the next few decades will still be the dominant position.
(3) New high-temperature alloys
Including powder high temperature alloys, titanium and aluminum intermetallic compounds, oxide dispersion strengthened high temperature alloys, corrosion resistant high temperature alloys, powder metallurgy and nano-materials and many other product segments.
① the third generation of powdered high temperature alloys to enhance the degree of alloying, so that it takes into account the advantages of the first two generations, to obtain a higher strength lower damage, powdered high temperature alloy production process is becoming increasingly mature, the future may be carried out from the following aspects: powder preparation, heat treatment process, computer simulation technology, dual-performance powder disk;
②Titanium and aluminum intermetallic compounds have been developed to the fourth generation, and gradually to the multi-trace and a large number of micro-element expansion of these two directions, Germany's Hamburg University, Japan's Kyoto University, Germany's GKSS Center, etc. have conducted extensive research, titanium and aluminum intermetallic compounds are now used in ships, biological medical, sporting goods field;
③Oxide-dispersion strengthened high-temperature alloys are part of the powder high-temperature alloys, which are being produced and developed by nearly 20 kinds of high-temperature strength and low stress coefficient, and are widely used in heat-resistant and oxidation-resistant parts of gas turbines, advanced aerospace engines, petrochemical reactors, etc.
④Corrosion-resistant high-temperature alloys are mainly used to replace refractory materials and heat-resistant steel in construction and aerospace applications.
High-temperature alloys are iron, nickel, cobalt-based, can work at high temperatures above 600 ℃ and under certain stresses for a long time a class of metal materials; and has a high temperature strength, good resistance to oxidation and corrosion resistance, good fatigue properties, fracture toughness and other comprehensive properties. High-temperature alloys are single austenite organization, with good organizational stability and reliability in various temperatures.
Based on the above performance characteristics, and high-temperature alloys are also known as "superalloys", which are widely used in aviation, aerospace, petroleum, chemical, naval, an important material. According to the base element, high temperature alloys are divided into iron-based, nickel-based, cobalt-based high temperature alloys. Iron-based high-temperature alloys can generally only be used at temperatures of 750 to 780°C. For heat-resistant parts used at higher temperatures, nickel-based and refractory metal-based alloys are used. Nickel-based high-temperature alloys occupy a special and important position in the entire field of high-temperature alloys, which are widely used to manufacture the hottest end parts of aviation jet engines and various industrial gas turbines.
Main classification
The traditional classification of high-temperature alloy materials can be done in the following three ways: by matrix element type, alloy strengthening type, and material forming method.
1、By type of matrix element
(1) Iron-based high-temperature alloys
Iron-based high-temperature alloy can also be called heat-resistant alloy steel. Its matrix is Fe element, adding a small amount of Ni, Cr and other alloying elements, heat-resistant alloy steel can be divided into martensite, austenite, pearlite, ferrite heat-resistant steel, etc. according to its normalization requirements.
(2) Nickel-based high-temperature alloys
Nickel-based high-temperature alloys contain more than half of nickel and are suitable for working conditions above 1,000°C. The use of solid solution and aging processes can result in a significant increase in creep resistance and compressive and yield strength. With regard to the analysis of high-temperature alloys used in high-temperature environments, the use of nickel-based high-temperature alloys far exceeds the range of iron-based and cobalt-based high-temperature alloys useful. At the same time, nickel-based high-temperature alloy is also China's largest production, the use of the largest amount of a high-temperature alloy. Many turbine engines turbine blades and combustion chambers, and even turbochargers also use nickel-based alloys as preparation materials. For more than half a century, the high-temperature materials used in aero-engines to withstand high temperatures from the late 1940s 750 ℃ to the late 1990s 1 200 ℃ should be said that this huge increase also prompted the rapid development of casting process processing and surface coating.
(3) Cobalt-based high-temperature alloys
Cobalt-based high-temperature alloy is based on cobalt, with cobalt content accounting for about 60%, while Cr, Ni and other elements need to be added to enhance the heat resistance of high-temperature alloys. Although this high-temperature alloy has better heat resistance, it is not used much because the production of cobalt resources in various countries is relatively small and processing is difficult. Usually used in high temperature conditions ( 600 ~ 1 000 ℃ ) and a longer period of time subject to extreme complex stress high temperature parts, such as the working blades of aircraft engines, turbine discs, combustion chamber hot end components and aerospace engines. In order to obtain better heat resistance, the general conditions to add elements such as W, MO, Ti, Al, Co in the preparation, to ensure its superior thermal fatigue resistance.
2、Alloy strengthening type
According to the type of alloy strengthening, high-temperature alloys can be divided into solid-solution strengthened high-temperature alloys and aging precipitation strengthened alloys.
(1) Solid solution strengthening type
The so-called solid solution strengthening type is to add some alloying elements to the iron, nickel or cobalt-based high-temperature alloy, the formation of single-phase austenite organization, solute atoms make the solid solution matrix dot matrix distortion, so that the solid solution in the slip resistance increases and strengthen. Some solute atoms can reduce the laminar dislocation energy of the alloy system and increase the tendency of dislocation decomposition, resulting in difficult cross-slip migration, and the alloy is strengthened to achieve the purpose of high temperature alloy strengthening.
(2) Aging precipitation strengthening
The so-called aging precipitation strengthening is a heat treatment process in which the alloy workpiece is solid solution treated, cold plastic deformation, and then placed at a higher temperature or room temperature to maintain its performance. For example: GH4169 alloy, the highest yield strength of 1 000 MPa at 650 ℃, the production of blades of the alloy temperature up to 950 ℃.
3、Material forming method
Through the material forming method is divided into: casting high temperature alloy (including ordinary casting alloy, single crystal alloy, directional alloy, etc.), deformation high temperature alloy, powder metallurgy high temperature alloy (including ordinary powder metallurgy and oxide dispersion strengthening high temperature alloy).
(1) Casting high-temperature alloys
Casting method directly prepared parts of the alloy material is called casting high temperature alloy. According to the alloy matrix composition, can be divided into iron-based casting high-temperature alloy, nickel-based casting high-temperature alloy and cobalt-based casting high-temperature alloy 3 types. According to the crystallization method, can be divided into polycrystalline casting high-temperature alloy, directional solidification casting high-temperature alloy, directional eutectic casting high-temperature alloy and single crystal casting high-temperature alloy and other four types.
(2) Deformed high temperature alloys
It is still the most used material in aero-engines and is widely used both at home and abroad, and the annual production of deformed high-temperature alloys in China is about 1/8 of that in the United States [2]. Take GH4169 alloy as an example, it is one of the main varieties with the largest range of applications at home and abroad. China is mainly in the turbine shaft engine bolts, compressors and wheels, oil dump discs as the main parts, with the increasing maturity of other alloy products, the use of deformed high-temperature alloys may gradually reduce, but in the next few decades will still be the dominant position.
(3) New high-temperature alloys
Including powder high temperature alloys, titanium and aluminum intermetallic compounds, oxide dispersion strengthened high temperature alloys, corrosion resistant high temperature alloys, powder metallurgy and nano-materials and many other product segments.
① the third generation of powdered high temperature alloys to enhance the degree of alloying, so that it takes into account the advantages of the first two generations, to obtain a higher strength lower damage, powdered high temperature alloy production process is becoming increasingly mature, the future may be carried out from the following aspects: powder preparation, heat treatment process, computer simulation technology, dual-performance powder disk;
②Titanium and aluminum intermetallic compounds have been developed to the fourth generation, and gradually to the multi-trace and a large number of micro-element expansion of these two directions, Germany's Hamburg University, Japan's Kyoto University, Germany's GKSS Center, etc. have conducted extensive research, titanium and aluminum intermetallic compounds are now used in ships, biological medical, sporting goods field;
③Oxide-dispersion strengthened high-temperature alloys are part of the powder high-temperature alloys, which are being produced and developed by nearly 20 kinds of high-temperature strength and low stress coefficient, and are widely used in heat-resistant and oxidation-resistant parts of gas turbines, advanced aerospace engines, petrochemical reactors, etc.
④Corrosion-resistant high-temperature alloys are mainly used to replace refractory materials and heat-resistant steel in construction and aerospace applications.