A Guide to the Materials and Methods Required for Additive Manufacturing (AM)

H.C. Starck has decades of experience using AM and refractory metals, which makes it an ideal partner for clients looking for present and future applications in these fields. Offering expertise regarding material selection, part design, process validation, and full-scale manufacturing, H.C. Starck can provide clients and users with cutting-edge solutions in the fast-paced AM industry.

Both powder and wire feedstocks are available in H.C. Starck’s range of refractory metals. The company can support various AM methods, with its repertoire of refractory metal parts covering all key markets.

Materials

H.C. Starck offers both powder and wire feedstocks which are customized according to AM standards, drawing on its hundred years of experience in the production and development of refractory metals. The firm specializes in the competency areas of W, Mo, Ta, and Nb (in both pure metallic and alloyed forms), thus ensuring that the customers obtain materials of top quality.

The company plays a holistic role, using its own feedstock materials to produce cutting-edge finished goods that are manufactured using the most relevant AM methods.

Methods

Ever since AM was introduced, many different process technologies have been launched using wildly disparate methods (since no one technique is suitable for every application). H.C. Starck is in close contact with its collaborators and customers to ensure that the best feedstock materials and methods are selected for a given application. The firm has seen great success in AM with refractory metals using a wide range of techniques.

Markets

H.C. Starck has a variety of refractory metal 3D printing technologies that allow customers to meet their needs in every end market, as well as take advantage of the benefits that only AM offers.

The customer portfolio presently includes Medical, Aerospace, Industrial, Nuclear and Defense. The company is always looking to expand its list of product offerings, by exploring new avenues in part design and innovation, and design parts for applications in markets that have not yet explored the benefits of using refractory metals.

H.C. Starck brings both wire and powder feedstock of the highest quality to its customers, with material properties that are tailor-made to meet every suitable AM technique.

Feedstock Solutions

H.C. Starck uses creative new manufacturing techniques to produce wire and powder feedstock in combination with a supply chain that operates as part of other vertical processes. These processes, added to the company’s experience with metallurgy, ensure the production of top-quality materials that meet the requirements of different applications in challenging environments.

This sophisticated technology makes it possible to manufacture custom feedstock from refractory metals to meet precise specifications and deliver optimal material properties and performance parameters for AM.

The Benefits of Powder

H.C. Starck’s powder feedstocks are specifically made to ensure they fulfill the needs of demanding AM technology. Thus, they need to have properties of a higher standard than conventional production specifications, including:

  • Extreme purity
  • High bulk density
  • Spherical powder grains
  • Outstanding flowability
  • Low oxygen
  • Optimization of PSD for particular printing techniques

Wire

H.C. Starck produces wire feedstock from its conventional range of refractory metals for processes involving directed energy deposition. Wire size and material can be optimized depending on the respective process and application.

The arc melting processes that are used to manufacture H.C. Starck materials are unique, and result in drastically-reduced levels of interstitial and volatile impurities. This makes these materials the preferred choice in all AM techniques that involve melting.

Customization

H.C. Starck has produced a large range of pure metal powders of varying particle size distributions that make it easy to fulfill the specifications of a given printing technique.

The company’s customized array of alloy powder products includes:

test test
Tantalum alloys Ta-3W, Ta-10W
Molybdenum alloys TZM, Mo-La, Mo-Re
Tungsten alloys WHA, W-Re
Niobium alloys Nb C-103

New materials, as well as new methods, are constantly being produced to meet the unique requirements of each customer.

Typical Properties of AM Powders

Property Unit Niobium Molybdenum Tantalum Tungsten
Purity % >99.95 >99.95 >99.95 >99.95
Mean Particle Size D50 μm 20-30 20-30 20-30 20-30
D10/D90 μm 10/40 10/40 10/40 10/40
Bulk Density g/cc 4 5 8 10
Hall Flow s/50g 14-16 8-10 5-9 5-8
Oxygen ppm 1500 400 300 250

Methods

H.C. Starck provides the necessary skills to choose the most relevant material and technique for each application, thus ensuring the highest customer value by balancing part costs, dimensional accuracy and performance.

3D Screen Printing

H.C. Starck uses a screen printing method - designed for refractory metals - which makes use of a metal printing paste applied in vertical layers to produce the specified geometry. This technique has proven successful in obtaining structures composed of complex grids.

This process is useful when printing features which are very small, and which have very low tolerance limits. The use of traditional powders ensures outstanding customer value.

Post-print sintering is an essential stage, in most cases, to finish the process. This results in metallurgical properties that are better than conventional powder metallurgy specifications. As a consequence, customers can exploit the advantages of AM without having to endure inferior material characteristics.

Selected 3D screen printed tungsten parts

Selected 3D screen printed tungsten parts

Binder Jet Printing

This method uses a powder bed and polymer adhesives, which are utilized to produce a bonding of the powder in layers. This technique provides many benefits to the customer; one of which being the shorter build times that are achieved due to the fact the printing layers are thicker than those used in the 3D screen printing technique.

This method also requires post-print sintering or infiltration to attain superior mechanical properties in the final product. This technology allows H.C. Starck to exceed ASTM B777 properties for tungsten heavy alloy, for example.

Binder jet printed tungsten heavy alloy component

Binder jet printed tungsten heavy alloy component

As 3D printing is among the most important areas of growth for H.C. Starck, the company is constantly expanding the range of product functionality and novel applications that utilize refractory metals by exploiting AM design.

Powder Bed Fusion

The best-known AM technique that involves metal parts is powder bed fusion. Here, layers of metal powders are spread to be fused together using high-energy laser or electron beams.

Powder bed fusion allows parts to be produced at full density, without compromising on the accuracy standards of the design. It is a preferred option for materials that can be used in an as-welded condition.

H.C. Starck makes full use of the advantages of powder-bed fusion to, for instance, create an incredible reduction in the size of the final product and a great improvement in its efficiency. One such design is the company’s Ta alloy heat exchangers, which are carefully modeled for chemical processing applications at an industrial level.

Cross sectional view of a high efficiency heat exchanger

Cross sectional view of a high efficiency heat exchanger

Directed Energy Deposition

Directed energy deposition is a technique based on directing either a metal powder or a metal wire to a specific location, wherein energy from a laser beam, electron beam or plasma arc is used to melt it and produce a fusion of the material.

This method has several advantages, such as high rates of deposition, as well as the benefit of being able to apply structures of AM material over a part already available. Its versatility also allows several gradient material structures to be produced within one part.

Direct energy deposition is thus capable of producing parts of great intricacy, and H.C. Starck has demonstrated this using porous Ta coated on Ti, which could be used for biomedical applications. This technique is also relevant in achieving rapid, thick coatings (e.g., tubular sputtering targets).

Ta tubular sputtering target

Ta tubular sputtering target

Markets

With high quality and consistent performance, H.C. Starck is an ideal partner for even the most critical AM refractory applications.

Radiation Imaging

H.C. Starck’s multifaceted AM product repertoire includes 3D products that are lead-free and specifically designed for complex-geometry collimators, as well as anti-scattering grids for CT scanners, SPECT, and gamma cameras.

The company’s range of refractory metals guarantees exceptional material properties, such as high radiation attenuation, high elastic modulus and high-temperature mechanical characteristics. These properties account for their widespread use throughout the medical technology industry, in applications such as:

  • Radiation or isotope shielding
  • Beam collimation
  • High-temperature X-ray technology

Aerospace and Defense

H.C. Starck is proud of its AM technology that provides high-performing parts for critical applications in Aerospace and Defense Industries such as ballistics, warheads, and propulsion.

The company has produced refractory metals with robust physical and mechanical attributes with high densities and an ability to withstand high temperatures, making them ideal for the most challenging applications and products. Some of which include:

  • High-temperature rocket nozzles and vanes
  • Counter-balance weights
  • Fragmentation warheads
  • EPF (explosively formed penetrator and MEFP

AM is entering more and more industrial areas each day. To keep H.C. Starck at the forefront of future design solutions, the company is constantly researching new materials and applications.

Biomedical

AM is already used in a host of medical applications. Its ability to form porous structures that promote bone osteointegration make it an advantageous choice for manufacturers in the field of biomedicine.

Moreover, its material properties can be fine-tuned to produce better implants, and the overall mass of the part is less.

H.C. Starck materials are highly compatible with biological materials. Some specific alloys of tantalum, tungsten, and molybdenum have received approval from the FDA and CE, for biomedical applications, for example:

  • Orthopedic, dental and spinal implants
  • Cardiovascular stents
  • Radiation imaging markers

Industrial

H.C. Starck materials offer high resistance to corrosion, are durable and easily workable, and offer optimal heat transfer properties. These ensure that they are the first choice in demanding chemical and pharmaceutical applications.

Demanding modern applications, such as heat treating, sintering, brazing, annealing, metalworking, and other thermal processing areas, demand new and innovative solutions in AM refractory metal production.

Industrial products include:

  • Condensers, heat exchangers, coils, pipe spools, and many types of components which may come into contact with harsh fluids
  • Fabricated components including complex parts designed for furnaces, crucibles, and heating elements

With over a century of manufacturing experience in refractory metals, as well as additional experience in 3D printing, H.C. Starck is a forerunner in the area of additive manufacture (AM) technology.

This information has been sourced, reviewed and adapted from materials provided by H.C. Starck Fabricated Products.

For more information on this source, please visit H.C. Starck Fabricated Products.

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