At the conception of metal 3D printing technology in the 90s, it was only possible to process a small range of materials. Since then, multiple advancements have enabled 3D printing of numerous metals, unleashing new applications with every breakthrough.
The first application used in metal 3D printing was rapid prototyping: the aerospace industry has also been using this technology for several years and industrial production in other industries is growing rapidly.
In this article, we will explore the most common metals used in 3D printing and discuss why exactly these metals meet the requirements.
Due to the relatively high costs of Additive Manufacturing (AM), one of the applications where it is feasible to use these methods is in high-performance equipment such as in the aerospace, defense or energy industries. Therefore, in this sector, many advancements have been carried out in recent years with materials like titanium, inconel, aluminium or steel.
Titanium-based alloys are known for a high specific strength, stiffness and corrosion resistance, making them popular in the aeronautical, biomedical and chemical industries . As seen in the table above, the ultimate tensile strength of these alloys is high compared to other high-performance materials; additionally, its density is only 4.4 g/cm3.
One of the challenges of processing titanium is its high reactivity at elevated temperatures; to prevent reactions with oxygen or nitrogen the process has to be carried under vacuum or in an argon atmosphere. Electron Beam Melting (EBM) is commonly used for processing titanium, due to its use of a vacuum processing chamber, and advancements in Selective Laser Melting (SLM) and Directed Energy Deposition (DED) have also enabled the use of titanium in recent years. Leading companies in the 3D printing sector such as Materialise and 3D Systems offer titanium AM services.
Aluminium and its alloys
Aluminium has been used in many industries such as aeronautical and automotive because of its lightweight, corrosion resistant and good mechanical properties. Until recently, the application of AM to aluminium alloys was restricted because they are ideally suited for low-cost production by traditional manufacturing technologies and AM did not seem to have an economic advantage.
Some of the challenges of 3D printing this material included high laser reflectivity and formation of oxides on the surface. Nowadays, 3D printing of aluminium is mostly done in small scale but big efforts are being made to improve the technology and reduce costs, so it is expected that aluminium will become one of the most important materials for 3D printing in the near future.
There is also a lot of interest in aluminium alloys such as AlSi (Aluminium Silicon) or FeAl (Iron Aluminide), which have improved mechanical properties maintaining a low weight thanks to the aluminium.
It is also possible to 3D print high-temperature-resistant metals such as inconel, which can work at temperatures as high as 1100ºC. These nickel-based superalloys also have high-strength and excellent corrosion resistance making them ideal for the aerospace and the energy industries. Furthermore, thanks to their good processability it is relatively easy to produce parts using various 3D printing techniques including SLM and DED.
Nickel-based superalloys can be used in, as mentioned in a previous article, gas turbine blades, where high-strength, temperature resistance and complex geometries are required.
Steel is one of the most affordable materials in 3D printing, it has high strength, a good range of working temperatures and it is easy to process thanks to its ductility. In fact, it is possible to process it with most of the metal 3D printing technologies like SLM, DED, and binder jetting.
It is even possible to 3D print steel at home; the company ColorFabb provides a steel filament that can be printed with an extrusion additive manufacturing method.
We can classify steels relevant for 3D printing into two different groups: tool steels and stainless steels. Most of the leading companies in the AM sector offer the possibility of producing steel parts. For example, the company Formetrix (formerly Additive Manufacturing business of NanoSteel) offers the service of 3D printing tool steels which can be used for making tools, dies bearings and gears. The type 316L stainless steel is the most common one used for 3D printing. A typical demonstration of its use is for making the compressor wheel of a turbocharger, which can be done using SLM or DED technology.
Copper and its alloys
Copper is a material known for its high thermal and electrical conductivity, which has a promising future in a wide range of applications. However, engineers have had to overcome many challenges when it comes to 3D printing this material. Copper is a very reflective material, which means that it reflects the laser beams commonly used to 3D print other metals such as steel or titanium.
To avoid this issue, researchers at Fraunhofer ILT used green light lasers for the process and it has already been possible to produce high-density parts with their technology. In the near future, it is also expected to be possible to produce objects with complex geometries unleashing a world of opportunities for engineers.
It is possible to 3D print copper-based alloys such as bronze and brass. Bronze and brass are commonly used in marine applications due to its resistance to salt and water corrosion. Recently, bronze samples have been fabricated by SLM  and Wire Arc AM . Additionally, superior mechanical properties compared to traditional cast samples were reported in both studies.
Silver, Gold and Platinum
Precious metal AM has applications in the jewellery, aerospace and electronics industries; however, the technology for processing these materials for high-performance parts is still under development and currently, it is only available in the jewellery industry. Most powder bed fusion companies can 3D print with precious metals such as silver, gold or platinum.
For example, the company EOS in collaboration with Cookson Precious Metals (CPM) has proved the use of AM for producing objects in gold, giving more freedom to jewellery designers and providing the opportunity to produce pieces with less material and more cost-efficiently using a powder bed fusion technique. Different blends of gold, silver, and other materials are used to produce differently coloured jewellery; for example, yellow gold (75% Gold, 12% Silver), red gold (75% Gold, 4.5% Silver), white gold (75% Gold, 3% Silver, 14% Palladium).
Other companies such as Materialise offer the possibility of producing precious metal objects using a 3D printing technology called Lost Wax Printing & Casting. This method consists of making a 3D printed wax model using stereolithography; next, the wax model is used for creating a plaster mould where the final object is made by a conventional casting process. By using this technology, gold, silver, bronze, brass and copper products can be made mainly for jewellery, detailed miniatures and sculptures.
Metal 3D printing is already offering multiple applications across several industries and, more importantly, the number of applications is continuously growing. Additionally, the different companies competing to provide 3D printing products and services are increasing their catalogue of materials available in order to find new clients and expand to new sectors.
In the next years, we can expect the 3D printing industry to keep the same growth path; metal 3D printing is finally ready to be the disruptive technology that we need.
Want to know more about additive manufacturing? Interested in market insights, opportunities for materials suppliers and trends? Check out this comprehensive page that covers it all:
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 “PHYSICAL AND CHEMICAL PROPERTIES OF THE PARTS MECHANICAL PROPERTIES OF THE PARTS As built Heat treated .”
 “Understanding 3D Printing Metal Material Nuances | Stratasys Direct.” [Online]. [Accessed: 08-Oct-2018].
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 “Materialise Launches the Next Innovation in Metal 3D Printing Software | Materialise.” [Online]. [Accessed: 25-Sep-2018].
 “Green Light for New 3D Printing Process – Fraunhofer ILT.” [Online]. [Accessed: 25-Sep-2018].
 S. Scudino et al., “Additive manufacturing of Cu–10Sn bronze,” Mater. Lett., vol. 156, pp. 202–204, Oct. 2015.
 D. Ding, Z. Pan, S. van Duin, H. Li and C. Shen, “Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing,” Materials (Basel)., vol. 9, no. 8, p. 652, Aug. 2016.
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