What material is high temperature alloy? What do high-temperature alloy materials mainly include?
High-temperature alloys are a type of alloy used in high-temperature, severe mechanical stress and oxidation and corrosion environments. With the development of science and technology, high-temperature alloys have gradually formed six relatively complete parts.
1. Deformed high temperature alloy
Deformed high-temperature alloy refers to a type of alloy that can be processed by hot and cold deformation, has an operating temperature range of -253 ~ 1320°C, has good mechanical properties, comprehensive strength and toughness indicators, and has high anti-oxidation and anti-corrosion properties. According to its heat treatment process, it can be divided into solid solution strengthened alloy and age strengthened alloy.
1. Solid solution strengthened alloy
The operating temperature range is 900~1300℃, and the maximum anti-oxidation temperature reaches 1320℃. For example, GH128 alloy has a tensile strength of 850MPa and a yield strength of 350MPa at room temperature; a tensile strength of 140MPa and an elongation of 85% at 1000°C; a durable 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. Aging-strengthened alloy
The operating temperature is -253~950℃, and it is generally used to make structural parts such as turbine disks and blades for aviation and aerospace engines. The alloy used to make turbine disks has a working temperature of -253~700°C and is required to have good high and low temperature strength and fatigue resistance. For example: GH4169 alloy has a maximum yield strength of 1000MPa at 650°C; the alloy temperature for making blades can reach 950°C. For example: GH220 alloy has a tensile strength of 490MPa at 950°C and a durable life of more than 40 hours at 940°C and 200MPa.
Deformed superalloys mainly provide structural forgings, cakes, rings, bars, plates, pipes, strips and wires for the aerospace, aviation, nuclear energy, and petroleum civil industries.
2. Casting high temperature alloys
Cast high-temperature alloys refer to a type of high-temperature alloys that can or can only be formed by casting methods. Its main features are:
1. Has a wider composition range. Since there is no need to consider 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 so that the γ' content reaches 60% or higher, so that the alloy can still maintain excellent properties at temperatures up to 85% of the melting point of the alloy.
2. Has a wider application field. Due to the special advantages of the casting method, high-temperature alloy castings with nearly net shape or no margin can be designed and manufactured with any complex structure and shape according to the use needs of the parts.
According to the service temperature of casting alloys, they can be divided into the following three categories:
Category 1: Equiaxed crystal cast high-temperature alloys used at -253~650°C. This type of alloy has good comprehensive properties over a wide range of temperatures, especially at low temperatures, where both strength and plasticity are maintained without degradation. For example, K4169 alloy, which is used in large amounts in aviation and aerospace engines, has a tensile strength of 1000MPa at 650°C, a yield strength of 850MPa, and a tensile plasticity of 15%; the endurance life under 620MPa stress at 650°C is 200 hours. It has been used to make diffuser casings in aerospace engines and complex structural parts for various pumps in aerospace engines.
Category 2: Equiaxed crystal cast high-temperature alloys used at 650 to 950 ℃. This type of alloy has high mechanical properties and hot corrosion resistance at high temperatures. For example, K419 alloy has a tensile strength greater than 700MPa and a tensile plasticity greater than 6% at 950°C; at 950°C, the ultimate strength limit for 200 hours is greater than 230MPa. This type of alloy is suitable for use as aircraft engine turbine blades, guide vanes and integrally cast turbines.
Category III: Directionally solidified columnar crystal and single crystal high-temperature alloys used at 950-1100°C. This type of alloy has excellent comprehensive properties and anti-oxidation and anti-hot corrosion properties in this temperature range. For example, DD402 single crystal alloy has a durable life of more than 100 hours under a stress of 1100°C and 130MPa. This is the hottest turbine blade material used in China and is suitable for making first-stage turbine blades for new high-performance engines.
With the continuous improvement of precision casting technology, new special processes are also constantly emerging. Fine-grain casting technology, directional solidification technology, and CA technology for complex thin-walled structural parts have greatly improved the level of casting high-temperature alloys and their application scope has continued to increase.
3. Powder metallurgy high temperature alloys
High-temperature alloy powder products are manufactured by using atomized high-temperature alloy powder, hot isostatic pressing or hot isostatic pressing and then forging. Using the powder metallurgy process, due to the small powder particles and fast cooling speed, the composition is uniform, no macrosegregation, and the grains are small, the hot processing 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 improved. Big improvement.
FGH95 powder metallurgy superalloy has a tensile strength of 1500MPa at 650°C and a durable life of more than 50 hours under a stress of 1034MPa. It is currently the highest strength plate powder metallurgy superalloy under 650°C working conditions. Powder metallurgy high-temperature alloys can meet the requirements of engines with higher stress levels and are the materials of choice for high-temperature components such as turbine disks, compressor disks and turbine baffles in engines with high thrust-to-weight ratios.
4. Oxide dispersion strengthening (ODS) alloy
It is a special high-temperature alloy formed by using a unique mechanical alloying (MA) process. Ultra-fine (less than 50nm) ultra-stable oxide dispersion strengthening phases at high temperatures are evenly dispersed in the alloy matrix. Its alloy strength can still be maintained under conditions close to the melting point of the alloy itself, and has excellent high-temperature creep properties, superior high-temperature oxidation resistance, carbon and sulfur corrosion resistance.
There are currently three main types of ODS alloys that have been commercially produced:
MA956 alloy can be used at temperatures up to 1350°C in an oxidizing atmosphere, ranking first among high-temperature alloys in terms of resistance to oxidation, carbon and sulfur corrosion. Can be used for lining the combustion chamber of aircraft engines.
MA754 alloy can be used at temperatures up to 1250°C in an oxidizing atmosphere and maintains very high high-temperature strength and resistance to medium-alkali glass corrosion. It is now used to make aero-engine guide gear rings and guide blades.
MA6000 alloy has a tensile strength of 222MPa and a yield strength of 192MPa at 1100°C; the 1000-hour endurance strength at 1100°C is 127MPa, ranking first among high-temperature alloys and can be used in aerospace engine blades.
5. Intermetallic compound high-temperature materials
Intermetallic high-temperature materials are a type of light-specific high-temperature materials with important application prospects that have been recently researched and developed. For more than ten years, basic research on intermetallic compounds, alloy design, process development and application research have matured, 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 have 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 steelness and excellent oxidation resistance and creep resistance. 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 and corrosion resistance, high strength at medium temperatures (less than 600°C), and low cost. It is a new material that can partially replace stainless steel.
