Nb C103 (Nb-10Hf-1Ti) is designed for extreme high temperatures and lightweighting. The king of high-temperature strength: The most distinctive feature of its performance curve is that above 1000°C, its specific strength (strength/density) far exceeds that of most nickel-based alloys. This is its irreplaceable core advantage.
Although the density figure is slightly higher than that of some nickel-based alloys, considering the absolute load it can bear at the same high temperature, its structural efficiency (light weight) is extremely outstanding. The vacuum nozzle extension section of the rocket engine (in space environment). With cooling (the combustion chamber side has a reducing atmosphere or cooling protection). A silicide anti-oxidation coating (such as R512E coating) must be applied, but this will increase the complexity of the process and reliability risks. The application scenarios are almost exclusively designed for the high-temperature, low-weight, short-term working components of spacecraft upper stage engines and attitude control engines.
If you need to manufacture components with complex shapes, thin walls, requiring a lot of welding, and with a working temperature below 1200℃, or for short periods of high temperature (< 5 minutes). For example: nozzle extension sections, attitude control engines. Select niobium 521 (Nb-5W-2Mo-1Zr-0.07C): If you need the components to work for a long time at temperatures ranging from 1200℃ to 1600℃, and have extremely high requirements for resisting creep deformation. For example: the nose cone of hypersonic aircraft, the inner lining of the combustion chamber, and the rocket thrust chamber that works for a long time.
Selection: Nb C103 is chosen only when the operating temperature exceeds 1100°C and weight is the primary constraint. The working environment is a vacuum or can be protected by reliable inert gas/cooling (or coating technology is up to standard). Typical components include satellite thrusters combustion chambers and radiation cooling nozzles for upper-stage rocket engines. The preferred condition for Nb521 is ≥ 1400°C, with a requirement for long-term anti-rust property, aiming for a balance between high-temperature strength and cost (such as for the new generation of aerospace engines). Both Nb C103 (Nb-10Hf-1Ti) and Nb 521 (Nb-5W-2Mo-1Zr-0.07C) are commonly used high-temperature niobium-based alloys in the aerospace field. C103 focuses on forming and welding properties, suitable for manufacturing complex components; Nb521 is strengthened by solid solution of W, Mo, Zr + carbide precipitation, and its high-temperature strength at 1600°C is 3.4-4.5 times that of C103, making it more suitable for ultra-high temperature long-term working conditions.
C103 can be welded by electron beam / argon arc welding. It can be easily processed into thin-walled and complex parts, and is suitable for manufacturing large-sized components. Nb521 has good heat processing properties and can be forged / rolled / spun. It is reliable in welding, but due to its high content of W and Mo, the processing difficulty is slightly higher than that of C103. Regarding the performance comparison between Nb C103 (Nb-10Hf-1Ti) and Nb 521 (Nb-5W-2Mo-1Zr-0.07C)，these two represent two different development directions of niobium alloys:C103 is the "benchmark for processing and welding performance"， while 521 is "the representative of high-temperature strength". C103 has excellent welding performance. It is one of the best-welded grades among niobium alloys and can be welded by electron beam welding and tungsten inert gas arc welding (TIG). The weld strength is high， and it is not prone to cracking， making it very suitable for manufacturing complex thin-walled components (such as thrust chambers). Its formability and cold/hot processing properties are both excellent， and it can be deep drawn， spun into complex shapes. The welding performance of Nb 521 is poor. Due to the presence of tungsten and molybdenum， cracks are prone to occur during welding， and the welding process requirements are extremely high. Usually， strict preheating and protection measures are required. Due to its high strength and hardness， the forming difficulty of 521 is greater than that of C103， and it is more dependent on hot processing (forging， hot rolling).
