High-temperature alloys are divided into three types of materials: 760 ℃ high temperature materials, 1200 ℃ high temperature materials and 1500 ℃ high temperature materials, with a tensile strength of 800MPa. In other words, it refers to high-temperature metal materials that work for a long time at 760–1500 °C and under certain stress conditions. It has excellent high-temperature strength, good oxidation resistance and thermal corrosion resistance, good fatigue performance, fracture toughness and other comprehensive properties. It has become an irreplaceable key material for the hot end components of military and civilian gas turbine engines.
Classification
760℃ high temperature material deformation superalloy
Deformed superalloy refers to a class of alloys that can be processed by hot and cold deformation, with a working temperature range of -253 to 1320 °C, good mechanical properties, comprehensive strength and toughness indicators, and high oxidation resistance and corrosion resistance. According to its heat treatment process, it can be divided into solid solution strengthened alloy and aging strengthened alloy. The first digit after GH indicates the classification number, namely 1, solid solution strengthened iron-based alloy 2, age-hardened iron-based alloy 3, solid solution strengthened nickel-based alloy 4, cobalt-based alloy after GH, the second, third, and fourth digits Numbers indicate sequence numbers.
1. Solid solution strengthened alloy
The operating temperature range is 900 to 1300 °C, and the maximum anti-oxidation temperature is 1320 °C. For example, the GH128 alloy has a room temperature tensile strength of 850 MPa and a yield strength of 350 MPa; a tensile strength of 140 MPa at 1000°C and an elongation of 85%, and a lasting life of 200 hours and an elongation of 40% at 1000°C and 30MPa stress. Solid solution alloys are generally used to make aviation and aerospace engine combustion chambers, casings and other components.
2. Age-strengthened alloy
The operating temperature is -253 to 950 °C, and it is generally used to make structural parts such as turbine disks and blades of aviation and aerospace engines. The working temperature of the alloy for making the turbine disk is -253 to 700 °C, and it is required to have 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, and the lasting life at 940℃ and 200MPa is more than 40 hours.
Deformed superalloys mainly provide structural forgings, cakes, rings, bars, plates, pipes, strips and wires for aerospace, aviation, nuclear energy, petroleum and civil industries.
760℃ 800MPa high temperature material casting superalloy
Cast superalloys refer to a class of superalloys that can or can only be cast to form parts. Its main features are:
1. It has 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 nickel-based superalloys, the γ’ content can be adjusted to 60% or higher, so that the alloy can still maintain good properties at temperatures as high as 85% of the alloy’s melting point.
2. It has a wider application field. Due to the special advantages of the casting method, it is possible to design and manufacture superalloy castings with nearly net shape or no allowance with any complex structure and shape according to the use needs of the parts.
According to the service temperature of casting alloys, it can be divided into the following three categories:
The first category: equiaxed crystal casting superalloys used at -253 ~ 650 ℃. These alloys have good comprehensive properties in a wide range of temperatures, especially at low temperatures, they can maintain strength and plasticity without decreasing. For example, K4169 alloy, which is used in aviation and aerospace engines, has a tensile strength of 1000 MPa at 650 °C, a yield strength of 850 MPa, and a tensile plasticity of 15%; at 650 °C, the durable life under 620MPa stress is 200 hours. It has been used to make diffuser casings in aero-engines and complex structural parts for various pumps in aerospace engines.
The second category: equiaxed crystal casting superalloys used at 650 to 950 °C. These alloys have higher mechanical properties and hot corrosion resistance at high temperatures. For example, K419 alloy, at 950℃, the tensile strength is greater than 700MPa and the tensile plasticity is greater than 6%; at 950℃, the lasting strength limit of 200 hours is greater than 230MPa. These alloys are suitable for use as aero-engine turbine blades, guide vanes and integrally cast turbines.
The third category: alloys such as directionally solidified columnar crystals and single crystal superalloys used at 950 to 1100 °C have excellent comprehensive properties, oxidation resistance and hot corrosion resistance in this temperature range. For example, the DD402 single crystal alloy has a durable life of more than 100 hours at 1100 ° C and a stress of 130 MPa. This is the turbine blade material with the highest temperature in China, and 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, and CA technology for complex thin-walled structural parts have greatly improved the level of casting superalloys, and their application scope has been continuously improved.
760℃800MPa high temperature material powder metallurgy superalloy
The products of superalloy powder are produced by the production process of atomized superalloy powder, hot isostatic pressing or hot isostatic pressing and then forging. Using powder metallurgy process, due to the fine powder particles and fast cooling speed, the composition is uniform, there is no macrosegregation, and the grains are small, the hot working performance is good, the metal utilization rate is high, and the cost is low, especially the yield strength and fatigue properties of the alloy are good. larger improvement.
FGH95 powder metallurgy superalloy, the tensile strength at 650℃ is 1500MPa; the lasting life under 1034MPa stress is more than 50 hours. It is a powder metallurgy superalloy with the highest strength level under the working condition of 650℃. Powder metallurgy superalloys can meet the requirements of engines with high stress levels, and are the materials of choice for high-temperature components such as turbine disks, compressor disks and turbine baffles in high thrust-to-weight ratio engines.
1200℃100MPa high temperature material oxide dispersion strengthened (ODS) alloy
It is a special high-temperature alloy formed by using a unique mechanical alloying (MA) process. Its alloy strength can still be maintained under the conditions close to the melting point of the alloy itself, and it has excellent high temperature creep performance, excellent high temperature oxidation resistance, carbon and sulfur corrosion resistance.
There are three main ODS alloys that have achieved commercial production:
The operating temperature of MA956 alloy can reach 1350 ℃ in an oxidizing atmosphere, ranking first in the oxidation resistance, carbon and sulfur corrosion resistance of superalloys. Can be used for aero-engine combustion chamber lining.
The MA754 alloy can be used in an oxidizing atmosphere at a temperature of up to 1250 °C and maintain a relatively high high temperature strength and is resistant to medium alkali glass corrosion. It has been used to make aero-engine guide gear ring and guide vane.
The tensile strength of MA6000 alloy at 1100℃ is 222MPa and the yield strength is 192MPa; at 1100℃, the lasting strength for 1000 hours is 127MPa, ranking first in superalloys and can be used for aero-engine blades.
Intermetallic High Temperature Materials
Intermetallic compound high-temperature materials are a class of light-weight high-temperature materials with important application prospects that have been recently researched and developed. 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 of Ti-Al, Ni-Al and Fe-Al series materials , mechanical properties and application research has made remarkable achievements.
Ti3Al-based alloy (TAC-1), TiAl-based alloy (TAC-2) and Ti2AlNb-based alloy have low density (3.8～5.8g/cm3), high temperature and high strength, high rigidity and excellent oxidation resistance, creep resistance, etc. Advantages, it can reduce the weight of structural parts by 35 to 50%. Ni3Al-based alloy, MX-246 has good corrosion resistance, wear resistance and cavitation resistance, showing excellent application prospects. Fe3Al-based alloy has good oxidation resistance and wear resistance, high strength at medium temperature (less than 600 ° C), and low cost. It is a new material that can partially replace stainless steel.
Ambient superalloys
In many fields 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.
development trend
The trend of superalloy development is to further increase the working temperature of the alloy and improve the ability to withstand various loads at medium or high temperature, and prolong the life of the alloy. As far as turbine blade materials are concerned, single crystal blades will enter a practical stage, and the comprehensive performance of directional crystal blades will be improved.
In addition, it is possible to manufacture multi-layer diffusion-bonded hollow vanes using chilled alloy powders to accommodate increased gas temperatures. As far as guide vanes and combustion chamber materials are concerned, it is possible to use oxide dispersion-strengthened alloys to significantly increase service temperatures. In order to improve corrosion and wear resistance, the alloy’s protective coating materials and processes will also be further developed.
