3D PRINTING OF TECHNICAL CERAMICS
Technical ceramics possess superior mechanical, electrical, thermal, biological, and chemical properties compared to most metals and polymers.
They are used for a wide range of specialized applications in various industries ranging from automotive, aviation, aerospace, electronics, energy to the medical industry.
These ceramics are distinguished into two main groups: oxides and non-oxides. The first group includes the metal oxides like alumina, zirconia, and silica. The non-oxide group consists of materials such as silicon carbide, silicon boride, and silicon nitride.
In this group oxide fibers are added to the ceramic mixture to enhance strength and reinforcement. Also making the final product withstand oxidation.
Alumina (aluminum oxide) is the most widely used and cheapest technical ceramic. Its properties such as high levels of hardness and resistance to temperature and corrosion make it suitable for a wide variety of applications.
Zirconia (zirconium dioxide) is based on a metallic element, zirconium. Main properties of zirconia include excellent thermal insulation, low thermal conductivity, and high resistance to crack propagation. They are widely used in dentistry applications and other medical devices.
Silica (SiO2) is commonly used for producing shells and cores in investment casting for aerospace and energy applications due to its thermal shock resistance and chemical dissolution properties.
Non-oxide ceramics are majorly used in extreme conditions like high heat. They also show high corrosion resistance, hardness, and oxidation resistance.
Silicon carbide is one of the hardest metals at the same time it is lightweight and resistant to acids. It is used in mechanical seals and pump parts, car brakes, clutches, and ceramic plates in bulletproof vests.
Boron carbide is particularly used in applications that require elevated temperature as it has an extremely high melting point of > 3000°C, high resistance to oxidation, and high thermal and electrical conductivity.
Silicon Nitride exhibits a very low density, a high fracture toughness, good flexural strength, and excellent thermal shock resistance. It is used in pumps, valves, and semiconductors
Having briefly discussed various technical ceramics, let us now look at the 3D printing techniques available to use these ceramics as a filament to manufacture parts.
Technical ceramics are hard to form using conventional production methods. Machining of ceramics is extremely difficult owing to their hardness and brittleness. Furthermore, creating a precise and dimensionally accurate part with ceramics is also a challenge.
Therefore, additive manufacturing is introduced in the field of ceramic manufacturing. Additive manufacturing techniques make it possible to produce parts with highly precise geometries that cannot be achieved using conventional machining or moulding techniques.
There are various additive manufacturing processes to manufacture ceramic parts. These include stereolithography, Selective Laser Sintering, and laminated object manufacturing. Ceramic feedstock is available in various forms as required for these processes.
Ceramic slurry or paste is used as a feedstock in stereolithography (SLA).
Photosensitive resins are mixed within a solid load of ceramic powder to form the slurry.
Layer by layer deposition takes place with help of a laser that polymerizes the slurry paste, forming the final ceramic component.
The parts are then subjected to a heat treatment which removes the resin (debinding) and densifies the ceramic by sintering. SLA is the most widely used technique to obtain an excellent surface finish.
Other additive manufacturing technologies that use ceramic pastes or slurries as a feedstock are Direct Light Printing (DLP) and Lithography-based Ceramic Manufacturing (LCM) technology.
SELECTIVE LASER SINTERING
SLS uses ceramic powder as a feedstock which is then deposited layer by layer and laser treated to form the final product. Post-processing takes place, similar to SLA process where the resin is burnt out and product is sintered.
LAMINATED OBJECT MODELING AND FUSED DEPOSITION MODELING
Additive manufacturing processes like LOM and FDM use solid ceramic filaments to manufacture parts.
3D printing of ceramics paves way for technological advances that were limited by the machining operations.