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Niobium Alloy
Niobium Alloy has good high temperature strength and low temperature plasticity, as well as excellent processing and welding performance, but poor oxidation resistance. Generally, the powder metallurgy method of vacuum high temperature sintering, electron beam furnace (EB), vacuum consumable electric arc furnace (VAR) vacuum smelting method is an ideal common method for preparing high-purity niobium alloy ingots.
| Physical properties of Niobium Alloy | ||
| Grade | Cb752 | C103 |
| Component | Nb-10W-2.5Zr-0.05Mo-0.15Ta-0.1Hf | Nb-10Hf-1Ti-0.7Zr-0.1W-0.1Mo-0.05Ta |
| Density /g.cm-3 | 8.83 | 8.86 |
| Melting point /℃ | 2349 | |
| Linear expansion coefficient /10-6K-1 | 4.5（1203℃） | 4.5（1203℃） |
| Recrystallization temperature /℃ | 1023~1371 | 1038~1316 |
| Annealing temperature /℃ | 982~1093 | 871 |
| Elongation brittle transition temperature /℃ | -196 | -196 |
Main chemical composition of Niobium-based Alloy (mass fraction)
| Grade | Chemical Composition / % | Chemical Composition / | |||||||||
| Nb | W | Mo | Ta | V | Hf | Zr | Ti | C | O | N | |
| C103Nb-10Hf-1Ti | Balance | 9~11 | ＜0.7 | 0.7~1.3 | ＜100 | ＜300 | ＜300 | ||||
| Cb752Nb-10W-2.5Zr | Balance | 9~11 | 2~3 | 10 | ＜200 | ＜200 | |||||
| Nb521 | Balance | 4.7~5.5 | 1.7~2.5 | 0.7~1.2 | |||||||
Choices of Niobium Alloy
Characteristics and applications of Niobium Alloy
| Grade | Characteristics and applications |
| Nb1Zr | Small thermal neutron capture cross section, strong resistance to liquid metal corrosion, used in atomic energy industry and high pressure sodium lamp industry |
| C103 | High temperature and high strength for the aerospace industry |
| Cb752 | High temperature and high strength for the aerospace industry |
| Nb-50Ti | Good superconductivity, used in superconductor technology; high strength, used in the aerospace industry |
Niobium alloy has a high melting point and still has high strength below 1650°C. However, it is easy to generate an oxide film (Nb2O5) without protection at high temperature. Therefore, in addition to improving the oxidation resistance of the base alloy itself, it is also necessary to apply a protective coating to ensure the high temperature performance of the alloy.
Classification of Niobium Alloy
Niobium alloys are generally classified according to service characteristics and strength. Among them, there are 5 types of structural niobium alloys:
1) Low strength niobium alloy
2) Medium strength niobium alloy
3) High strength niobium alloy
4) Low density niobium alloy
5) Interstitial compound strengthened high strength niobium alloy
Niobium alloys classified according to their use characteristics are:
1) Elastic niobium alloy
2) Superconducting niobium alloy
3) Anti-oxidation- niobium alloy
4) Constant expansion niobium alloy
1) Low strength niobium alloy
Using niobium as the base metal, adding IV B group Ti, Zr, Hf and other elements to form a solid solution strengthened alloy, such as Nb-1Zr, Nb-10Hf-1Ti-07Zr, at room temperature, its strength σb=320~420MPa, elongation The rate of δ=20%~40%, and the fusion welding performance is good. Under the temperature of 0.37~0.47 T and vacuum conditions, after 1000h aging treatment, the ductility-brittle transition temperature (DBTT) is still lower than room temperature. Such niobium alloys are used in turbopump nuclear liquid alkali metal delivery pipelines for inter-hole nuclear power plants, as well as for attitude control of spacecraft, satellites, missiles, and thrust chamber body extensions for motor engines.
2) Medium strength niobium alloy
Taking niobium as the base metal, adding no more than 10% of tungsten, molybdenum, tantalum, vanadium, titanium, zirconium, hafnium and other metal elements and a small amount of carbon to form solid solution strengthening and a small amount of ZrO2 (rhombic structure) and (Nb) , Zr) C precipitation strengthening phase combined niobium alloy, such as Cb752 (Nb-10W-2.5Zr), C-129Y (Nb-10W-10Hf-0.1Y) and so on. At room temperature, the strength of these alloys is σb=450~600MPa, and the elongation δ=20%~30%, and there are still quite high strengths between 1000~1400℃. Since these alloys are sensitive to interstitial elements such as hydrogen, oxygen, and nitrogen, their DBTT is relatively high, and the DBTT in the welded state is generally above room temperature. This type of niobium alloy is suitable for the manufacture of riveted and fastened components, such as skins, bolts, nuts, etc.
3) High strength niobium alloy
Taking niobium as the base metal, adding a large amount of tungsten, molybdenum, tantalum, titanium, zirconium and other metal elements and a small amount of carbon and other elements to form a niobium alloy that combines high solid solution strengthening and (Nb, Zr) C precipitation strengthening, such as FS -85 (Nb-28Ta-10W-1Zr) etc. This kind of alloy has quite high tensile strength, creep strength and fatigue strength in the range of 1300~1600℃. This type of niobium alloy is suitable for the manufacture of high temperature components.
4) Low density niobium alloy.
With niobium as the base metal, a large amount of tungsten, molybdenum, tantalum, vanadium, titanium, zirconium, chromium, tin and carbon are added to form a combination of high solid solution strengthening and precipitation strengthening of compounds such as Ti3Al, (Nb, Zr)C. Niobium alloy. The density of these niobium alloys at room temperature is 5.9~6.9g/cm³, which is 70%~80% of the density of niobium; if the surface of the alloy is not coated with anti-oxidation coating, it can be used in the atmospheric environment of 550~800℃ without Oxidized, under the condition of adding anti-oxidation coating, it can be used in the atmospheric environment of 800~1300 ℃, and when the surface coating is damaged, the alloy matrix will not be burned through and destroyed immediately.
5) Interstitial compound strengthened high-strength niobium alloy
Today’s aerospace engineering technology requires a niobium alloy that maintains the plasticity of the existing high-strength niobium alloys, but also has higher strength. The most thermodynamically stable chemical compound is added to the niobium base metal. These niobium alloys have high strength in the range of 1100~1400℃, such as the room temperature strength σb=300MPa and elongation δ=20% of Nb-0.3%ZrO2 (mass fraction) in the recrystallized state at 1300℃/1h; Strength σb=120MPa at 1200℃, elongation δ=36%. This type of niobium alloy has good working plasticity at room temperature and above 800 ℃, as well as alloy ingots.
| The stress relief annealing temperatures(keep warm for one hour) for several niobium alloys are as follows | |||||
| Alloy | Nb-10W-1Zr-0.1C | Nb-15W-5Mo-1Zr-0.1C | Nb-10W-2.5Zr | Nb-1-W-28Ta-1Zr | Nb-10W-10Hf |
| Stress relief annealing temperature,℃ | 1200 | 1200 | 1000 | 1000 | 1000 |
| The recrystallization temperatures of several niobium alloys are as follows | |||
| Alloy | Recrystallization temperature range, ℃ | Alloy | Recrystallization temperature range, ℃ |
| Nb-5Zr | 980-1300 | Nb-4V | 930-1200 |
| Nb-10Ti-5Zr | 970-1150 | Nb-5Mo-5V-1Zr | 1100-1370 |
| Nb-10W-1Zr-0.1C | 1150-1430 | Nb-1Zr | 1000-1280 |
| Nb-27Ta-10W-0.1Zr | 1150-1430 | Nb-15W-5Mo -1Zr-0.1C | 1540-1760 |
| Nb-10W-2.5Zr | 1150-1430 | Nb-10W-10Hf | 980-1200 |
| Nb-10Hf-1Ti | 870-1200 | Nb -28W-10Ta -1Zr | 1310-1370 |
| Nb-10W-1Hf | 980-1200 | ||
Niobium alloy tubes, rods and wires are processed by extrusion, forging, rolling and drawing, and are usually supplied in the recrystallized annealed, stress relieved annealed and cold worked conditions.
Applications of Niobium Alloy
Many unique properties of Niobium Alloys determine that it is a multi-purpose functional material. In the electronics, steel, metallurgy, chemistry, cemented carbide, atomic energy and aerospace industries, modern strategic weapons, superconducting technology, scientific research, medical equipment, and even arts and crafts and decoration industries, all involve tantalum metal, alloys and compounds The wide range of applications. Niobium is mostly used in industries and superconducting technologies such as steel, ceramics, and nuclear energy.
Niobium alloy can maintain high strength and good processing performance at high temperature. It can be made into thin plates and parts with complex shapes. Therefore, in some hypersonic aircraft, spacecraft, satellites, missiles and supersonic low-altitude rockets can be used as the preferred thermal protection materials and structural materials.
The superconducting transition temperature of niobium is high, and niobium compounds and alloys can be used to make superconducting materials.
Niobium alloys also have unique applications in chemical industry, medicine and other industries.
