Niobium alloy

A niobium alloy is one in which the most common element is niobium.

Alloys used for the production of other alloys

The most common commercial niobium alloys are ferroniobium and nickel-niobium, produced by thermite reduction of appropriate mixtures of the oxides; these are not usable as engineering materials, but are used as convenient sources of niobium for specialist steels and nickel-based superalloys. Going via an iron-niobium or nickel-niobium alloy avoids problems associated with the high melting point of niobium.

Superconducting alloys

Niobium–tin superconducting wire from the ITER fusion reactor, which is currently under construction.

Niobium-tin and Niobium-titanium are essential alloys for the industrial use of superconductors, since they remain superconducting in high magnetic fields (30 T for Nb₃Sn, 15 T for NbTi); there are 1200 tons of NbTi in the magnets of the Large Hadron Collider, whilst Nb₃Sn is used in the windings of almost all hospital MRI machines.

Aerospace rivets

Niobium-titanium alloy, of the same composition as the superconducting one, is used for rivets in the aerospace industry; it is easier to form than CP titanium, and stronger at elevated (> 300°C) temperatures.

Refractory alloys

Niobium-1% zirconium is used in rocketry and in the nuclear industry. It is regarded as a low-strength alloy.

C-103, which is 89% Nb, 10% Hf and 1% Ti, is used for the rocket nozzle of the Apollo service module and the Merlin vacuum engines; it is regarded as a medium-strength alloy. It is typically produced using gas atomization or plasma atomization techniques. It is particularly used in additive manufacturing (3D printing) and powder metallurgy processes. Due to its corrosion resistance and high thermal efficiency, C103 helps reduce material waste and environmental pollution.

High-strength alloys include C-129Y (10% tungsten, 10% hafnium, 0.1% yttrium, balance niobium), Cb-752 (10% tungsten, 2.5% zirconium), and the even higher strength C-3009 (61% niobium, 30% hafnium, 9% tungsten); these can be used at temperatures up to 1650°C with acceptable strength, though are expensive and hard to form.

Niobium alloys in general are inconvenient to weld: both sides of the weld must be protected with a stream of inert gas, because hot niobium will react with oxygen and nitrogen in the air. It is also necessary to take care (e.g. hard chrome-plating of all copper tooling) to avoid copper contamination.