3D Printing Materials: Metals
Following our introduction of the different 3D printing technologies, today we will be talking about the metals used in 3D printing. To begin, it is important to note that metals are widely used in the aeronautics, automotive and bio-medical industry and use processes such as Selective Laser Sintering (SLS), Direct Metal Laser Sintering (DMLS) or E-Beam (EBM).
This material is an excellent compromise between lightness and solidity. In addition to being resistant to corrosion, it can also be welded. Compared to steels, it is less resistant and more sensitive to high temperatures. It is mainly used in areas where weight is essential such as in mechanical parts of racecars, aeronautics, aerospace, bicycles, etc.
It is rarely present in a pure state and is found more often as an alloy with metals that improve its physical and mechanical properties, such as silicon and magnesium. A typical example is AISi10Mg Aluminum, which is proposed by the German manufacturer EOS in powder form. This makes it possible to manufacture solid and complex parts.
Even in research and development, gallium is used as an alloy with 25% indium, to print objects from small metal bubbles or from self-supporting metal cables to join electronic components, for example. What makes this alloy special is that not only can it melt at a low temperature of 85.46° F (29.7° C), the two metals also harden in air while the inside remains liquid, enabling the print to be flexible.
Here is a video made by a team of researchers at the University of North Carolina who are working on printing this material:
The price remains the main barrier when wanting to commercialize this material for 3D printing use.
Being one of the most common metals in the industry for manufacturing all types of parts, it is no surprise that steel was the first metal used in 3D printing. The French company Phoenix (bought by 3D Systems), had developed a patent specifically for steel.
Stainless steel is quite present in everyday life, mechanical industries, and medicine. It has good metal properties and makes it possible to obtain a polished and bright surface. Several players in additive manufacturing offer this material such as EOS, ProMetal or ExOne.
It is also possible to print bronze or gold parts using stainless steel as a base material. The layers of stainless steel powder are coated with glue to inject bronze into the printing, for example.
The company EOS offers the Maraging Steel MS1 steel, which is used in the manufacturing of tools or molds, thanks to its strength and resistance to breaking.
Titanium is the flagship of medicine and aerospace, thanks to its excellent composition of both strength and weight, in addition to its high resistance to corrosion and biocompatibility.
As with aluminum, titanium alloys have improved mechanical properties and chemical behavior. In the market, there are the Ti6Al4V by EOS, the Ti6AL4V Grade 5 and the Ti6AL4V ELI Grade 2 by Arcam.
3D printing makes it easier to manufacture titanium parts and avoids the impurities obtained with traditional techniques during the welding phase. However, a major disadvantage of this material is its high cost, as it is around 50 times greater than that of steel.
Like titanium alloys, cobalt-chromium alloys, such as CoCrMo, are widely used in medicine for the manufacturing of prostheses in both orthopedics and odontology (thanks to its stiffness, smoothness, wear-resistant surface condition and lack of corrosion). In addition, the automotive and aerospace industries use some highly heat-resistant cobalt-chromium-molybdenum alloys.
EOS offers CobaltChrome MP1 and SP2 alloys that are resistant to high temperatures at 1,112° F (600° C). On the other hand, Arcam markets the ASTM F75, which is also widely used for the production of tools and molding.
We previously saw that it is possible to add glue to inject bronze and gold into a printed object made of steel. There is also another way of printing with these metals, which is through a molten metal cast. This cast is a mold made with lost wax, with the finishing being done by hand.
This method is widely used in jewelry and in the manufacturing of small objects. One of the problems and limitations to this molding is that you must take into account the thin shapes that need to be avoided, as well as ensuring that you have a minimum thickness of 0.8 mm to 1 mm for the walls must be respected.
The finishing phase is the key to a good surface rendering, especially for silver coins. With gold, it is possible to obtain different shades of colors (pink, white and yellow).
Here is a video to help you understand the applications of 3D metal printing:
To wrap up, it is important to note that today it is possible to modify the atomic structure of the metal during printing. By doing this, you will have a more rapid and uniform solidification, which can result in a more rigid and resistant metal.
Fun fact: It is now possible to print metal at home. Vader Systems has introduced a consumer printer at the Maker Fair in New York in 2013.