Niobium alloy can be divided into structural alloy, corrosion resistant alloy and functional precision alloy. Aerospace application is the most structural alloy, and structural alloy is divided into high strength, medium strength and low strength, low density niobium alloy and clearance compound strength of high strength niobium alloy. Since "PEST" oxidation will occur in Nb under high temperature aerobic environment, it is necessary to coat the surface with oxidation resistant coating, and coating technology has become the key technology to ensure the application of niobium alloy. The following will focus on the high strength niobium alloy, low density niobium alloy.
The development of niobium alloy began in the 1950s and was greatly developed during the "space race" in the 1960s. Both the United States and the Soviet Union developed a variety of niobium alloys for space engines. Alloys such as SCB-291 (NB-10TA-10W), FS-85 (Nb-28Ta-10W-1Zr), Nb-1Zr, Nb-5Zr and Nb752 (Nb-10W-2.5Zr) have been developed in the United States to meet the needs of different parts of space engines. These alloys mostly use hafnium, tungsten, tantalum as strengthening elements. The most widely used alloy is Wah Chang's C103 alloy, which played an important role in The Hercules III, Apollo manned moon landing spacecraft and so on, and is still used today.
The Soviet Union developed a series of р ARM-5, р ARM-6, 5 м м, and other alloys, most of which are tungsten, molybdenum, zirconium as strengthening elements, and have been applied in liquid rocket engines. Nb521 also uses 600-1000ppm C element to form the second phase of NbC and ZrC, and adopts the solution + precipitation strengthening method to comprehensively improve the alloy strength and machining performance. Compared with C103 alloy, niobium-tungsten alloy has similar density (8.6-9.0g·cm-3) and better high-temperature strength. But because of the addition of a large number of W, Mo and other strengthening elements, ingot room temperature strength is higher, plasticity is poor, in the ingot processing using high temperature extrusion, in order to refine the ingot grain. After extrusion, the plasticity of alloy ingot is greatly improved, and rods, plates, forgings and spinning parts of required specifications can be obtained by forging, rolling, spinning and other processing methods.
Through nearly 20 years of research and development, niobium-tungsten alloy has been widely used in the domestic aerospace field to manufacture liquid rocket engine combustion chamber, thrust chamber and other high-temperature components. In addition, niobium-tungsten alloy fasteners are used in the thermal structure of some new engines to ensure the stability and reliability of the whole structure.
