Metal printing is one of the most promising industries of the future. It avoids the mass of disadvantages inherent in classical casting or stamping. A special powder is used to produce a part from which a billet is obtained. It is this powder that gives the final product this or that physical property.
The main characteristics of metal 3D printing
Metal 3D printers are used in large productions. They find their application in design bureaus, engineering workshops and research institutes. In civilian areas, metal printers are placed in medical centers.
Additive printing technology makes it possible to make complex interwoven structures in the form of a single part. For example, in 2020, NASA made “space fabric”. The material resembles the texture of chain mail with a very intricate inner pattern. The difference between the ancient armor and the modern material lies in the production technology. The chainmail was woven by weaving each link by hand. Space cloth was printed in one pass.
Metal products made on a 3D printer are valued for their characteristics:
- High strength of the finished piece. The density figures are 1.5 times higher than metal casting.
- Complex geometry. Intricate shapes of fancy geometry can be printed. For example, to make a high-strength chain without welding points.
- Wide range of alloys and materials. From aluminum to titanium.
- Rough surface of the product. In some cases, this is a plus rather than a minus.
- No stress in the metal, which is almost impossible to achieve in casting.
- A wide range of post-processing.
A separate line can be singled out in the cost of the finished part. Powder printing does not require special tooling as, for example, for casting. The required part is loaded into the program memory, and after a short time it appears from the printer.
There are several basic printing technologies:
- SLM – basic metal powder printing technology. The part is formed by sintering the material in the inner chamber of the printing device under the influence of the laser.
- DMP – an almost complete analogue of the previous technology. This solution can be found in 3D Systems printers.
- EBM is a technology in which the sintering of the powder takes place under the action of an electron-beam gun.
There is a private variation of the SLM technology called DMLS. The second variant means that the powder particles are heated to lower temperatures. The material does not go into a liquid state.
Synopsis. SLM printing technology was developed by Wilhelm Meiners, Konrad Wissenbach, and Dieter Schwarz and Matthias Fockele. Subsequently, founder Dieter Schwarz left to join SLM Solutions GmbH, which is one of the world’s leading 3D metal printers.
Operator behind a 3D printer from SLM Solutions
Types of metal powders for 3D printing
There are about 20 most well-known materials based on metal powder, which are used to solve different problems. For example, a technologist can take a titanium alloy to create the frame of the future assembly, and make the walls and insides of the mechanism out of aluminum. The result is a strong and light structure with the necessary performance characteristics.
Metal powders are actively used in the aviation, automotive, aerospace industries. With the help of additive technologies engineers create complex assemblies and innovative parts. The main types of powders are: titanium, steel, aluminum, cobalt-chromium, nickel.
Important! By saying “powder” we mean an alloy based on one of the above metals.
Titanium powder for 3D printers
The most common alloy is Ti6Al4V. It has excellent performance characteristics. Titanium alloy is rightly considered one of the strongest and most durable among other metals. The finished product has a density of 4500 kg/m. Tensile strength is up to 900 MPa. The maximum temperature is up to +1100 °C. The material is valued for its lightness and reliability. It is often used in aircraft and space industries.
Tool steel is used everywhere. The most common alloys are 1.2343, 1.2344, 1.2367, 1.2709. This material is used to make casting molds, various tools such as cutters, measuring dies and tooling. Steel alloys usually contain from 0.7 % of carbon. This makes the material more ductile. The end products get increased strength and hardness.
Aluminum and alloys
This material is considered one of the cheapest lithium alloys on the market. The most common powders are of the AlSi10Mg, AlSi12 type. This material has several advantages: high resistance to corrosion, thermal conductivity, fluidity. This alloy conducts electric current well. It is used in manufacture of large thin-walled components.
CoCr alloy is one of the most popular materials for making parts in aviation and rocket industry. The alloy has high mechanical properties. Various units and parts with complex geometry are made of it. Cobalt-chromium alloys are used in the production of clasp dentures.
The main peculiarity of nickel is its ability to dissolve other metals without losing its strength. It is this characteristic that makes it one of the most common in various industries. For example, NiCr alloys are used to make heat-resistant blades for jet engines. Some nickel alloys are comparable in melting point to titanium powder. Their upper threshold reaches as high as +1100 °C. The most common nickel alloys are Inconel 625, Inconel 718, Inconel 939, Invar 36, NX.
Other alloys and metals
Among the other common metals, two other groups can be distinguished:
- Stainless steel alloys. Powders with at least 12% chromium content. These include 15-5PH, 17-4PH, AISI 410, AISI 304L, AISI 316L, AISI 904L.
- Nonferrous metal alloys. Metallic powder with copper or tin added. Such materials include CuSn6, CuSn10.
- There are also less demanded alloys, for example, based on tungsten.
Interesting! There are powders made of precious metals. Cooksongold, in particular, has created platinum powder for printing jewelry. The finished pieces get 950 proof and boast better mechanical characteristics.
Production of powder for a 3D printer
The production cost of material for “filling” the 3D printer on metal is higher than, for example, filament or photopolymer. This explains the price of the finished product. In the factory, hot metal melt is “atomized” with a jet of gas, water or plasma to produce a powder. This greatly complicates and increases the cost of production.
Interesting! In 2019, a group of Russian scientists from the National Research University of MISIS developed a new way to produce titanium and aluminum powder. A planetary mill is used in its production. It is like a semi-finished product that is brought to the desired mechanical properties already in the process of printing.
The operators of the SLM machines use the powder several times. In particular, they recycle scrap, as well as reuse it in support re-production. And this is about 10% of the total mass of the printed workpiece. The leftovers are crushed and recycled on special machines – atomizers.
There are a large number of powders based on metal alloys. All of them solve one or another problem. You need to select the material based on the physical, mechanical and chemical properties of the final product.