HOW DOES 3D PRINTING SILICON CARBIDE WORK?

Silicon Carbide is a ceramic material consisting of the chemical elements silicon (Si) and carbon (C) that is highly versatile in its use due to some exceptional properties. These include high thermal stability, high thermal conductivity, electric conductivity, chemical resistance, and extreme hardness. There are different kinds of Silicon Carbide (SiC) ceramics. The following article will deal with the so-called SiSiC, meaning silicon infiltrated Silicon Carbide.

Silicon Carbide is used in a range of high-tech industries including the metallurgical industry, semiconductors, aerospace, the defense industry (typically for body armor), in refractories and as a general hard-wearing ceramic. It is also one of the certified materials for CONCR3DE’s Blue 3D printers for metals and technical ceramics. In this article, we are going to take a closer look at the manufacturing process of Silicon Carbide in binder jetting, its applications, and properties.

Binder jetting is a 3D printing technology in which a powder and binder are fused on a print bed. A 3D printer deposits a thin layer of Silicon Carbide powder on which a binder is jetted using a cross section of a CAD model. Layer by layer, the final shape is built up in this manner and, after completion, retrieved from the print box. All non-used powder can be fully reused. After the parts have been printed, they have to undergo a series of post-processing treatments. First, they have to be left in the printing box for drying, and then placed in an oven. Afterwards, the powder is removed from the parts. Next, they are placed in a kiln to undergo post-processing treatments that involve the application of heat. One of which is sintering, which is done at 1.860°C. Lastly, the parts are infiltrated with liquid silicon to decrease their porosity and form secondary Silicon Carbide of free carbon and silicon, to increase the Silicon Carbide content.

There are several reasons why Silicon Carbide is useful for a range of applications:

Producing Silicon Carbide parts with CONCR3DE’s binder jetting technology is advantageous for various reasons. It is fast, no milling is required producing zero waste, and each product can be fully customized. There are more reasons why binder jetting is the right technology for manufacturing Silicon Carbide:

Speed of production and reduced lead times
Silicon Carbide printed through binder jetting drastically reduces lead times and speeds up production. Traditional manufacturing methods involve time-consuming processes like tooling and shaping, causing delays. In contrast, binder jetting deposits material layer by layer, streamlining production and significantly shortening lead times. Additionally, as Silicon Carbide is a very hard material, shaping it leads to high wear of the tooling used and significant cost in replacing worn tooling. This can be prevented by using 3D printing.

Off the shelf solution with Armadillo Blue
We offer a complete off-the-shelf solution with our Armadillo printer, Silicon Carbide powder, and binder. This proven standardized solution allows you to embark on your Silicon Carbide printing journey instantly, eliminating the hassle of testing and sourcing equipment and materials separately.

Precision for large parts
Binder jetting is the technology of choice for manufacturing large, precise parts with Silicon Carbide. For this reason, it is ideal for producing large machine parts that have complicated shapes. With ourelph large-scale printer, you can print parts up to 2 x 1 x 1 meter in size. Even larger options are available on request.

Unlocking complex geometries
Engineers and designers can use binder jetting technology to build large, extremely detailed items with high precision. Traditional manufacturing methods that involve pressing cannot shape tiny details.

Waste-free production
Silicon Carbide binder jetting is an additive manufacturing method that allows for the complete recycling of unbound powder. This way, the production process becomes virtually free from waste. While this recycled powder may have slight differences from the "raw powder", it remains highly suitable for printing. In fact, you can use approximately 90% recycled powder for a new print. The other recycled powder can be used for the next print after that, as only 10% fresh powder is required. This significantly reduces waste and resource consumption.

Versatility with particle-filled binders
While our 3D printers (including Armadillo) predominantly operate with aqueous binders, they can also be used with particle-filled binders, which typically increase material density. If you are interested in particle-filled binder, do not hesitate to contact us.

Partnership with WZR, leaders in ceramics 3D printing materials
Our collaboration with WZR, the leading service provider in the development of technical ceramics for 3D printing, guarantees that you are on the front row for updates and breakthroughs in this area. CONCR3DE and WZR continue pushing the boundaries of what Silicon Carbide binder jetting can achieve.

Law enforcement: reinventing body armor with Silicon Carbide

This Silicon Carbide body armor was made using the Armadillo Blue 3D printer, in collaboration with WZR

The mechanical qualities of Silicon Carbide make it a good material for personalized protection applications, particularly body armor or anything that involves high resistance. Due to its hardness (9.5 on the Mohs hardness scale), Silicon Carbide offers unmatched protection against blunt force attacks or ballistic impacts. This makes the material very useful for police officers and other law enforcement personnel.

What truly sets binder jetting apart is its flexibility. No molds are required, allowing the creation of personalized body armor tailored to individual users. Whether it is optimizing fit, protection, or comfort, Silicon Carbide body armor can be uniquely designed to meet the specific needs of each user.

Refractory industry: Silicon Carbide burner

In the realm of high-temperature applications (refractory), Silicon Carbide (SiC) is an important material, typically used for burners in the oil and gas industry. Silicon Carbide's exceptional rigidity endures soaring temperatures, up to 1.200°C, rendering it an indispensable choice. In the combustion process, Silicon Carbide components preserve their structural integrity, ensuring precise and consistent performance over time. This capability is important in enhancing the burner's endurance and resistance to thermal fluctuations, ideal for all applications where heat resistance is necessary, such as industrial furnaces and kilns.

This image shows 30 small burners loaded into CONCR3DE’s NOAH print preparation and management software, for the Armadillo Blue XL. At a layer height of 200 micron, this print job will take 7 hours and 50 minutes. With double precision, with 100-micron layers, the job will be completed in a little over 15 hours.

In this section, we will take a closer look at the step-by-step process from powder mixture to a Silicon Carbide object ready for use.

1. Printing with Silicon Carbide powder and particle-free binder
Initially, an engineered Silicon Carbide powder is placed in the print box of the CONCR3DE 3D printer. This mixture is carefully applied layer by layer and bound together using a particle-free, water-based binder. This binder is not only environmentally friendly, but also safe for human handling, thus reducing its environmental impact. The printing time varies depending on the layer height and height of the object(s). At a layer height of 100 microns, printing an entire Armadillo print box takes up to a maximum of 20 hours, while at a layer height 200 microns it lasts 10 hours. The Silicon Carbide mixture is environmentally friendly and can be used without health risk.

For more specialized applications, CONCR3DE offers a particle-filled binder. It was designed to increase the density of the parts with the aim of enhancing their mechanical characteristics. Contact us for more info on this binder.

2. Utilizing the CONCR3DE Infrared (IR) Heater
During the printing process, the CONCR3DE IR heater is automatically used after each layer to facilitate the binding and solidification of the printed layers and increase the green strength of the parts.

3. Drying inside the printer
Once the printing is complete, the printed parts remain inside the printer overnight. The duration of this drying phase depends on the size of the print, until the object reaches sufficient green strength. To preserve the printed parts, they are kept within the Depowdering Box, a convenient and practical solution developed by CONCR3DE. The Depowdering Box allows for subsequent post-processing treatments with the excess (recyclable) powder still supporting the part, until the parts reach enough strength to be handled.

4. Initial drying in an oven
The printed parts are placed in an oven and dried at 120°C to achieve the final bending strength of 7 MPa, making the objects handleable.

5. Depowdering and further post-processing
After drying, the parts are carefully depowdered using brushes and compressed air, ensuring that any residual powder is removed. CONCR3DE provides solutions like our Depowdering Station and the depowdering kit to largely automate and facilitate the depowdering process. We will explain the depowdering process in more detail in an upcoming publication. If you would like more information about CONCR3DE’s depowdering solutions, please contact us.

6. Debinding and pyrolysis
The parts then undergo a crucial heat debinding and pyrolysis heat treatment process in a kiln. This involves heating the object in an oxygen-free environment, essentially "cooking" it to extract carbon: the binder that forms the green part is burnt out and only its carbon content remains. n. The aim here is to increase the residual carbon content, as secondary SiC is formed from silicon and carbon atoms.

7. Silicon infiltration in graphite furnace
The next step involves sintering, in which the part is under inert conditions at 1860 °C. Sintering increases the density of the parts.heating the part in a graphite oven under partial pressure, whilst placed in a silicon filled crucible. The oven is heated to a temperature between 1500 and 1650 degrees Celsius. This melts the silicon. The atmosphere in the oven and porous nature of the SiC green part means allow the liquid silicon to infiltrate the SiC part through capillary action. Gases and air are displaced from the SiC part and the liquid silicon reacts with the present carbon to form additional silicon carbide. The part is then left to cool. A fully dense part SiSiC part is formed and can then be post processed further via polishing, grinding or other methods.

8. Optional: methods to increase SiSiC density
Different applications require different densities. Silicon carbide has a higher density than silicon, meaning a higher silicon carbide content vs silicon content is typically desired. This can be achieved via two strategies: having a higher green density of silicon carbide and by having more liquid silicon react with carbon in the furnace, and therefore more carbon must be added to the green parts before oven infiltration. A higher green density is achieved by achieving a high packing rate of silicon carbide powder. This can be achieved by controlling the particle size distribution of the initial powder mixture and compaction when depositing the powder – for example by making use of the large roller diameter in both the Armadillo and Elephant system. An even higher green density can be achieved with a particle filled ink. A higher carbon content can also be achieved in several ways. One method is to directly add carbon powder to the powder formulation. Another strategy is to dip green parts in phenolic resin and to then go for an additional debinding/pyrolysis step, possibly repeating this process multiple times till the correct amount of carbon remains in the part. At CONCR3DE we are happy to support customers in achieving the best 3D printed SiSiC material for your application. By tweaking powder composition and post processing we are able to achieve densities between 2,7 and 3,1 g/cm3. The image above shows several SiC parts in green state. The darker green bodies have embodied carbon in the powder mixture

One of the advantages of binder jetting technology is its material versatility - from metals and stone-like materials to technical ceramics such as Silicon Carbide. With our Armadillo Blue printer, producing high density Silicon Carbide parts is now easier than ever. This off-the-shelf solution enables anyone who is interested in Silicon Carbide production to make it a reality without the need for a proprietary process and lengthy research and development.

This material can be applied to multiple industries, from defense to refractory to semiconducts and more. Printing Silicon Carbide with binder jetting proves to be an excellent choice for a multitude of reasons. The powders can be fully recycled, there is no shrinkage during post-processing, and the geometries enabled by binder jetting significantly reduce post-assembling procedures. If you are interested in binder jetting, Silicon Carbide, or our particle-filled binders, do not hesitate to contact us or call our team at +31 85 060 6171.