About Niobium Alloys

image_pdfimage_print

Niobium alloys are made of niobium as the matrix with other elements. The niobium is a refractory metal with a melting point of 2,467°C. It has high specific strength in the temperature range of 1,093~1,427°C. Compared with tungsten alloys and molybdenum alloys, niobium alloys have good plasticity and excellent machining and welding properties, so they can be made into thin plates and parts with complex shape used as thermal protection and structural materials for the aerospace and aviation industry.

Niobium and niobium alloy, with good corrosion resistance to molten alkali metals, small absorption section of atomic thermal neutron (1.1 barns) and good compatibility with nuclear fuel, can be used as nuclear reactor materials. With excellent superconducting properties, niobium-titanium alloy (such as Nb-50Ti) and Nb3Sn compound are practical superconducting materials. Some niobium-titanium and niobium-zirconium alloys, with good constant elasticity, no ferromagnet, corrosion resistance and other comprehensive properties, can be made into the elastic elements of special purposes. Niobium and some niobium alloys have excellent corrosion resistance in most chemical mediums and lower cost than the tantalum, so they can be used as corrosion-resistant parts in chemical and textile sectors, etc.

From the mid-1950s to the early 1960s, two types of niobium alloys of excellent oxidation resistance and high strength were primarily developed. Later, niobium alloys of middle strength and good performance in machining and welding began to develop. Besides, the research on antioxidant protection coating of niobium alloys was strengthened. China started to study on production techniques of niobium in 1958, and began to conduct the industrial production of niobium in 1963, already produced niobium alloys of various grades such as low-strength and middle-strength, etc.

Niobium alloys still have good plasticity at low temperatures (-196°C). Compared with molybdenum and tungsten, niobium alloy elements have various kinds with high dosage. There are more than ten kinds of niobium alloys obtained by the industrial-scale production. Niobium alloys as structural materials are mainly divided into three categories: high-strength alloys (e.g. Nb-30W-1Zr, Nb-17W-4Hf-0.1C and Nb-20Ta-15W-5Mo-1.5Zr-0.1C), middle-strength alloys and low-strength high-plasticity alloys.

Niobium alloys, used as additives of iron-, nickel- and zirconium-based super alloys, can improve the strength of super alloys. Niobium is suitable for structural materials of the reactor and coating materials of nuclear fuel in the atomic energy industry as well as thermal protection and structural materials in the aviation and aerospace industry. Niobium has similar capacitance with tantalum, but its capacitance is greater per unit volume for smaller density. In addition to niobium powder, some capacitors also use niobium alloy powder, hydrogenated niobium powder or hydrogenated niobium alloy powder. Superconducting materials, such as niobium-titanium alloys and niobium-zirconium alloys as well as niobium-tin compounds and germanium-aluminum-niobium compounds, are used not only for the electricity transmission, electricity generation, production of superconducting magnets and fusion control, but also for spacecraft navigation devices, electromagnetic propulsion equipments of high-speed diving vessels as well as superconducting and ultra-class high-speed trains.

As for the acid corrosion-resistant property, niobium is better than zirconium, while poorer than tantalum. It can be used for the heat exchanger, condenser, filter and mixer, etc. Niobium carbide can be used alone or be in combination with tungsten carbide or molybdenum carbide, as hot forging dies, cutting tools, turbine blades of jet engine, valves, tail skirts and rocket nozzle coating. Alloy steel containing niobium has high strength and good toughness with resistance to cold quenching, widely used in the oil pipeline.