Niobium Alloy

The main mechanical niobium combinations showed up in the mid 1950's, when new branches of innovation required materials equipped for working at temperatures above 1000°C. Notwithstanding a high softening point, niobium combinations have great mechanical properties and low thickness in respect to alloys made out of other high-dissolving metals (molybdenum, tungsten, and tantalum). The cold-brittleness limit of low niobium alloys is below the temperature of liquid nitrogen. These properties make possible the use of niobium alloys for thermally stressed parts in rockets, spacecraft, and special-purpose aircraft. A low thermal neutron capture cross section and good durability in contact with liquid-metal heat-transfer agents make niobium alloys valuable construction materials for atomic reactors. Niobium alloys are resistant to many acids and other chemical reagents. However, they oxidize upon heating above 400°C in air and other oxidizing media; therefore, they must have protective coatings for operation under such conditions. At 1100°C, the rate of oxidation of niobium alloys in air is 30–120 g/(m2 · hr); for unalloyed niobium the rate is 300–350 g/(m2 · hr). Niobium alloys with silicide protective coatings oxidize at 1100°C at a rate of 0.2–0.4 g/(m2 · hr).