High-temperature alloys: main materials used in aerospace
I. Overview
1. Composition of high-temperature alloys
High-temperature alloys are based on iron, nickel, and cobalt. The other main elements are chromium, aluminum, titanium, tungsten, molybdenum, etc. As a first-class metal material, they can work above 600°C and under certain stress conditions for a long time. They have high temperature strength and resistance. It has multiple advantages in terms of oxidation, hot corrosion resistance, fatigue performance, fracture toughness, etc.
2. Application of high temperature alloys
High-temperature alloys are widely used in aerospace, nuclear power, automotive industry, gas turbines, petrochemicals and other fields.
From the application scenarios of the global high-temperature alloy market, the aerospace field has long ranked first, accounting for more than 56% of the market demand, and is mainly used in the manufacturing of aerospace engines and aerospace fasteners.
2. Classification of high temperature alloys
1. High-temperature alloys are divided into: according to basic elements:
Iron-based high-temperature alloys: have lower operating temperatures, 600~850°C, and are generally used in parts of engines with lower operating temperatures, such as turbine disks, casings, shafts and other parts.
Nickel-based high-temperature alloys: have the highest operating temperature, about 1000°C, and are widely used to manufacture the hottest parts of turbojet aero engines and various industrial gas turbines, such as turbine blades, guide vanes, turbines, etc.
Cobalt-based high-temperature alloy: The operating temperature is about 950°C. It has good castability and weldability. It is mainly used as guide blade material. Due to the low cobalt resources, this type of alloy is expensive.
2. High-temperature alloys are divided into: according to manufacturing process:
Deformed high-temperature alloy: The operating temperature is 600-1000°C. It is generally used in compressor disks and turbine disks in engines. It has relatively low strength and good plasticity, thermal processing and weldability.
Casting superalloys: can be subdivided into three categories: equiaxed crystal superalloys, directionally solidified columnar crystal superalloys and single crystal superalloys.
1) Equiaxed superalloy: The operating temperature is 1000°C. It adopts traditional investment casting method and has relatively low temperature bearing capacity. It is mainly used in the rear blades of low-pressure turbines. It has a wide range of applications and accounts for 0% of all castings. 60-70% of components, but the additional profit of the product is low.
2) Directionally solidified cylindrical superalloy: The operating temperature is 1000-1100°C. It is manufactured using directional solidification technology and has relatively high temperature-bearing capacity. It is mainly used in the working blades of the first few stages of low-pressure turbines, as well as the first and second stages of high-pressure turbines in some engines. Class 1 rotor blades, the application scope is limited to rotor blades, and the additional profit of the product is higher.
3) Single crystal superalloy: The operating temperature is 1200°C. It is manufactured using directional solidification and crystal selection technology. It has the highest temperature-bearing capacity. It is mainly used in high-pressure wheel blades of advanced engines and the first two stages of low-pressure turbine blades. The scope of application is limited to working blades. Products The highest additional profit.
New high-temperature alloys: refers to high-temperature alloy materials produced through new manufacturing processes, mainly including powder high-temperature alloys and dispersion-strengthened high-temperature alloys (ODS).
1) Powder high-temperature alloy: The use temperature is 1100°C. The high-temperature alloy is atomized into powder, and then hot isostatic pressing or hot isostatic pressing and forging is used to produce high-temperature alloy products. It has high metal utilization rate and low cost. It has low temperature characteristics and relatively high temperature-bearing capacity. It is currently mainly used in turbine discs and turbine blades. It is an excellent material for high-temperature components such as turbine discs, compressor discs, and turbine baffles in engines with high thrust-to-weight ratios.
2) Dispersion-strengthened high-temperature alloy (ODS): with an operating temperature of 1200°C, it is made using a similar powder metallurgy process and has high temperature-bearing capacity. It is mainly used in flame tubes, guide vanes and turbine blades.
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