Tungsten (W) is a metal with a wide range of uses, the largest of which is as tungsten carbide in cemented carbides. Cemented carbides (also called hardmetals) are wear-resistant materials used by the metalworking, mining, and construction industries. Tungsten metal wires, electrodes, and/or contacts are used in lighting, electronic, electrical, heating, and welding applications. Tungsten is also used to make heavy metal alloys for armaments, heat sinks, and high-density applications, such as weights and counterweights; superalloys for turbine blades; tool steels; and wear-resistant alloy parts and coatings. Tungsten composites are used as a substitute for lead in bullets and shot. Tungsten chemical compounds are used in catalysts, inorganic pigments, and high-temperature lubricants.

   The word tungsten means "heavy stone" in Swedish. The chemical symbol for tungsten is W which stands for wolfram. The name came from medieval German smelters who found that tin ores containing tungsten had a much lower yield. It was said that the tungsten devoured the tin "like a wolf". Pure tungsten metal was first isolated by two Spanish chemists, the de Elhujar brothers in 1783. Tungsten is a greyish-white lustrous metal, which is a solid at room temperature. Tungsten has the highest melting point and lowest vapor pressure of all metals, and at temperatures over 1650°C has the highest tensile strength. It has excellent corrosion resistance and is attacked only slightly by most mineral acids.

W (pure Tungsten)

    Pure tungsten is a steel-gray to tin-white metal. Very pure tungsten can be cut with a hacksaw,  forged, spun, drawn, and extruded. The impure metal is brittle and can be worked only with difficulty. Tungsten has the highest melting point of all metals, and at temperatures over 1650oC has the highest tensile strength. The metal oxidizes in air and must be protected at elevated temperatures. It has excellent corrosion resistance and is attacked only slightly by most mineral acids. The thermal expansion is about the same as borosilicate glass, which makes the metal useful for glass-to-metal seals.

   Tungsten and its alloys are used extensively for filaments for electric lamps, electron and television tubes, and for metal evaporation work; for electrical contact points for automobile distributors; X-ray targets; windings and heating elements for electrical furnaces; and for numerous spacecraft and high-temperature applications. High-speed tool steels, Hastelloy(R), Stellite(R), and many other alloys contain tungsten. Tungsten carbide is of great importance to the metal-working, mining, and petroleum industries. Calcium and magnesium tungstates are widely used in fluorescent lighting; other salts of tungsten are used in the chemical and tanning industries. Tungsten disulfide is a dry, high-temperature lubricant, stable to 500C. Tungsten bronzes and other tungsten compounds are used in paints.

   Advantages of W for high temperature applications: high melting temperature; low vapour pressure; sufficiently high electrical resistance; low thermal expansion combined with good thermal conductivity; high E-modulus.

Applications:

 Components for the high temperature furnace construction

Parts for the manufacture of quartz glass

Electrodes for the joining technology and lighting industry

Tungsten-Lanthanumoxide

   The content of La₂O₃ is 1 weight%. The structure and therefore the properties depend strongly on the material deformation ratio.

Advantages compared to pure W: better creep resistance; higher recrystallization temperature for high deformation ratio; better high-temperature strength; higher ductility (better machinability);

Advantages compared to Tungsten-Thoriumoxide (for applications as an electrode material): not radioactive; maximum emission rate at lower temperatures; lower burn off-rate of the electrodes.

Applications:

Components for the manufacture of quartz glass

Electrodes for discharge lamps in the lighting industry

TIG welding electrodes

Tungsten-Thoriumoxide

   It is a tungsten alloy doped with thoriumoxide which is mainly used as an electrode material.

   Advantages compared to pure W: higher recrystallization temperature: higher thermal stability; lower electron emission work; better machinability.

   Disadvantage: radioactivity.

   Applications:

TIG welding electrodes

Electrodes for discharge lamps in the lighting industry

Electrodes for plasma melting, plasma welding, plasma spraying (thermal spraying)

Emission cathodes for electron tubes

Tungsten-Ceroxide

   It is a tungsten alloy doped with 2 weight% of CeO₂ and is mainly used in the welding technology.

   Advantages compared to pure W: lower electron emission work.

   Advantages compared to Tungsten-Thoriumoxide: not radioactive; lower burn-off rates of the welding electrode; longer service life.

Applications:

TIG welding electrodes

Grainstabilized Tungsten

   By doping the tungsten with aluminium-potassium silicate followed by intense deformation it is possible to produce tungsten alloys with a high form stability and a high corrosion resistance against various molten metals or high grain stability. It has a nominal chemical composition of 0.005 K in weight% or 0.002 K in weight%.

   Advantages compared to pure W: higher recrystallization temperature; elongated grain structure after recrystallization (WVM for Ø/thickness < 1 mm); grain stability; higher creep stability (WVM for Ø/thickness < 1 mm); higher arc stability.

   Applications:

Electrodes for discharge lamps in the lighting industry

Boats and coils for resistive evaporation

Stationary anodes for the medical technology

Heating elements for the high temperature furnace construction

Grainstabilized Thoriated Tungsten

   By doping the thoriated tungsten with aluminium-potassium silicate followed by high deformation it is possible to produce tungsten alloys with a high grain stability. They are used as electrode materials for various applications. The nominal chemical composition in weight%: 1 ThO₂, 0.004 K or: 2 ThO₂, 0.0015 K.

   Advantages compared to ungsten-Thoriumoxide: stability against grain growth; higher arc stability.

   Disadvantages: radioactivity.

   Applications:

Electrodes for discharge lamps in the lighting industry

Tungsten-Rhenium

   By alloying the tungsten with rhenium it is possible to produce tungsten alloys with a higher strength, lower ductile-to-brittle-transition temperature and increased ductility. Flokal manufactures the standard alloys W₅Re and W₂₆Re.

   Advantages compared to pure tungsten: lower transition temperature from brittle to ductile condition; no brittleness in recrystallized condition; higher recrystallization temperature; better weldability; higher thermal stability; higer creep stability up to 1800 °C.

   Disadvantages compared to pure W: more difficult to machine

   Applications:

Propulsion nozzles for the aerospace industry

Focal paths for X-ray targets in the medical technology

Thermoelements up to 2000 °C for the high temperature furnace construction

Different tungsten products & alloys