Tungsten, whose translation means “heavy stone,” is a highly versatile refractory transition material with a silver-gray shine, extracted from naturally occurring Wolframite and Scheelite ores from the Earth’s crust. It has the highest melting point (~ 3422°C) and the lowest thermal expansion coefficient of all known metals. Of all periodic table elements, its melting point is only second to carbon (~ 3550°C). It also possesses an extremely high boiling point of around 5700°C that is close to the temperature of the sun’s outer shell – the photosphere.

The element symbol for the refractory metal tungsten

Tungsten has very high thermal conductivity and a very low coefficient of thermal expansion, making it dimensionally stable even under extremely high temperatures. It has a very high density, at par with some rare and expensive metals like gold, platinum, plutonium, and more than twice that of steel. These properties classify tungsten as one of the hardest, most stable and most heat-resistant metals known. In addition, its exceptionally high melting temperature renders it an ideal candidate for high-temperature applications. Due to these superior properties, tungsten is used in a variety of industries.

Due to its unique properties, machining pure tungsten poses a significant manufacturing challenge. Therefore, it is typically alloyed with copper, nickel, and iron to form tungsten-heavy alloys (WHA). The first processing of WHA dates to the mid-1930s to replace lead in radiation shields. The resulting multicomponent alloys exhibit substantially improved mechanical properties and machinability. Improved machinability eases their industrial manufacturing and allows the fabrication of intricate shapes for critical engineering applications.

  1. C. Starck Solutions has unparalleled expertise in developing advanced materials and offers innovative, cutting-edge refractory metals-based products. H.C. Starck Solutions manufactures tungsten employing advanced manufacturing capabilities that include additive manufacturing, powder-based metallurgy, sputtering, and hot and cold rolling. We ensure that our tungsten-based robust products span a broad spectrum of critical industries, ranging from aerospace, medical applications, and semiconductors to defense, nuclear, and off-shore drilling.

Applications of Tungsten

Aerospace and Defence

Due to their superior thermal properties, high-temperature strength, and excellent creep and corrosion resistance, tungsten alloys are routinely used in aerospace applications that involve extremely challenging environments. These applications involve blistering high temperatures, as well as low temperatures, such as in deep-space probes.

 

Due to the high density, tungsten-heavy alloys are ideal candidates for balance weight applications in aircrafts such as the rotor blades of helicopters, missile guidance systems, control surfaces of aircraft elevators, rudders, and ailerons. Tungsten alloys also provide the most effective shield against radiation.

 

The Medical Industry

H.C. Starck’s tungsten solutions are widely used in medical sciences, due to their exceptional radiation management capacity. We provide state-of-the-art components such as shafts, stationary and rotating anodes, bar materials, screws, etc., for X-ray tubes, anti-scatter grids, and multi-leaf collimators; to dynamically manipulate beam shape and deliver accurate focus during radiation therapy. Tungsten alloys are also utilized for shields and beam collimators in the Atlas Detector of the Large Hadron Collider. Our experience with extensive precision machining enables us to produce ultra-thin tungsten plates with exceptional flatness and surface finish. These plates are a key component of the detector plate assemblies used in CT scanners.

In terms of the nuclear medicine field, significant danger to human life can result from radioactive leaks. To ensure personnel safety, imaging applications require optimum radiation shielding. We develop advanced tungsten alloys for radiation shielding technologies employed in nuclear medicine and molecular imaging. The x-ray and gamma radiation absorption efficiency of tungsten alloys is 50% higher than conventional lead due to the high density of tungsten alloys.

 

Inherently, dense tungsten alloys attenuate specific wavelengths of electromagnetic radiation, thereby delivering extremely safe therapeutic and diagnostic treatments. Typical radiation shielding applications include components for brachytherapy, syringe covers for radioactive isotope injections, isotope source containers for transporting radioactive materials to cancer treatment hospitals.  Tungsten-based materials are also used in gamma camera collimators and SEPTA plates as anti-scatter grids in PET scanners.

 

Off-shore drilling applications

Tungsten’s radiation shielding capability is employed in off-shore drilling applications. Tungsten alloys are used to surround data logging instrumentation and isotopes that are used to locate oil deposits. Highly dense tungsten alloys also facilitate their use in confined sinker bar applications, where they are attached to the down-hole logging tool assemblies. This added weight allows a channeled descent through the dense borehole fluids.

Semiconductor and thin-film applications

Tungsten’s improved machinability results in substantially lower amounts of pull-outs and chips during processing, making it ideal for fabricating sophisticated engineering components through precision machining. Due to its high electrical conductivity and low diffusivity across the neighboring layers, it is an integral component of thin-film transistors deployed in TFT-LCD screens. We also produce ultra-high pure tungsten for coating applications via sputtering.

 

Due to its wet chemical inertness, tungsten is deposited in “contact holes” connected to the transistor source and drain. Tungsten also acts as a filler between successive metal layers — known as the tungsten plug process. When subjected to mechanical stresses or electric currents, tungsten atoms do not move, thereby offering reliable metal interconnects in semiconductors.

Additive manufacturing

H.C. Starck Solutions is heavily involved in the Additive Manufacturing (AM, also known as 3D printing) of pure tungsten and tungsten-heavy alloys. More specifically, we deploy AM for prototyping intricate engineering components having small geometries. We utilize ultra-high pure alloy powders possessing high bulk density, high flowability, and optimum particle size distribution.

 

Our state-of-the-art manufacturing capabilities guarantee outstanding dimensional accuracy, finish, and product performance. Using advanced AM processes such as 3D screen printing, binder jet printing, powder bed fusion, and directed energy deposition, we produce quality products like complex-geometry collimators, anti-scatter grids (for gamma cameras and CT scanners), ballistics and warheads, porous components (for enhancing bone osteointegration), improved lightweight implants and high-temperature heat treatment metal products. These products span a varied spectrum of markets such as aerospace and defense, biomedical applications, radiation imaging, and chemical processing.

 

 

 

 

 

 

 

 

 

 

References

  1. https://www.hcstarcksolutions.com/tungsten
  2. https://www.hcstarcksolutions.com/additive-manufacturing-industry/
  3. https://www.hcstarcksolutions.com/aerospace-defense/
  4. Skoczylas et al, Microstructure and Properties of Tungsten Heavy Alloy Connections Formed during Sintering with the Participation of the Liquid Phase, Materials, 13, 4965, 2020.
  5. https://www.hcstarcksolutions.com/3-column-news/tungsten-alloys-medical-applications/
  6. https://www.hcstarcksolutions.com/wp-content/uploads/2019/11/Radiation-Shielding-for-Nuclear-Medicine-052019-Web.pdf
  7. Applications of Advanced Refractory Metal Products in Cancer Treatment, Source: https://www.azom.com/article.aspx?ArticleID=9074
  8. Applications of High Density Tungsten Alloys in Oil and Gas Production, Source: https://www.azom.com/article.aspx?ArticleID=12080
  9. http://www.enigmatic-consulting.com/semiconductor_processing/CVD_Fundamentals/films/W_WSi.html