SiCeram and Spectrum Filaments are introducing an innovative series of ceramic materials for use in filament extrusion (FFF) 3D printing technology. The four new specialized filaments, which include silicon carbide, silicon nitride, zirconia and alumina, position themselves as the first commercial solutions for 3D printing of advanced ceramic filaments using common desktop 3D printers.
The basis for this collaboration, is SiCeram GmbH’s innovative processes for manufacturing high-performance ceramic components. Thermoplastic feedstocks consisting of ceramic powders and polymers allow unique shape forming technologies analogous to polymers: injection molding, extrusion and warm pressing. With support from Spectrum Filaments, a manufacturer and supplier of high-quality filaments for generic filament extrusion 3D printers, the companies are bringing these very interesting materials to the market.
3D printing is a relatively new additive forming technology for ceramic components. It finds its application mainly in the fabrication of small series and highly complex geometries, with internal hollow spaces, which cannot be produced by other manufacturing techniques. One key advantage of 3D printing is the increased freedom in choosing over-size factors, in order to adapt different shrinkage values during sintering. An adaption of linear shrinkage for conventional shape forming technologies such as dry pressing or injection molding always means high costs for modifying the necessary tools. In the case of 3D printing, an additional component is simply printed using modified over-size factors.
The ceramic filaments for 3D printing are based on a polyamide as binding phase, which distinguishes them from other filaments for 3D printing using metal powder. These are generally based on relatively toxic POM. The ceramic filament print at very low temperatures, between 150°C-170°C with a bed temperature of 40°C-50°C.
Shape forming by the printer is followed by the usual processing steps such as de-binding, sintering and hard machining, if necessary. It is always feasible to machine the printed components in green state in order to minimize hard machining. By using a thermoplastic recipe the green components exhibit a high green strength and thus can be worked with almost no risk of damages.
All 3D models that will be presented next week at Formnext 2019 were printed on a BCN3D Sigma 3D printer, which confirms that materials are suitable for a desktop 3D printing environment.
SiCeram and Spectrum Filaments manufacture filaments for 3D printing based on some of most common materials in advanced ceramics. These include:
Silicon Carbide SSiC:
SSiC is extremely hard and exhibits excellent corrosion resistance over the whole pH-range. The strength at 1,500 °C is higher than at room temperature. The material can be applied in air up to 1,550 °C and up to 1,800 °C in inert atmosphere. The thermal conductivity of SSiC is very high with 120 W/mK as compared to stainless steel with 30 W/mK. SSiC is an electrical semi-conductor. Its high compression strength is 4,000 MPa.
Silicon Nitride Si3N4:
Si3N4 exhibits higher strength and fracture toughness than SSiC. The very low coefficient of linear thermal expansion leads to a high thermal shock resistance. Si3N4 is an electrical insulator and its thermal conductivity is 30 W/mK. The wettability of Si3N4 by non-ferrous metals and glass melts is very low thus qualifying it as tooling material. The maximal operating temperature lies in the range of 1,300 – 1,400 °C.
Aluminum Oxide Al2O3:
Al2O3 exhibits lower strength than SSiC und Si3N4. The strength at 1,000 °C is ca. 60 % lower than at room temperature. Al2O3 is an electrical insulator and a fairly good heat conductor (ca. 20 – 30 W/mK). The corrosion resistance in the acidic range is good (pH < 7), but poor in the basic range (pH > 7).
Zirconium Oxide ZrO2:
ZrO2 exhibits a high strength at room temperature and due to the crack induced transformation toughening a very high fracture toughness. Due to its high coefficient of linear thermal expansion (10*10-6K-1) ZrO2 can be bonded to stainless steel without any problems. The corrosion resistance in the range pH < 7 is good, in the range pH > 7 very insufficient.