AGC Ceramics Co, Ltd, Tokyo, Japan, and Voxeljet AG, Friedberg, Germany, have partnered to qualify Brightorb™, a high-performance ceramic material for Additive Manufacturing. Brightorb, originally developed by AGC Ceramics, is composed of spherical sand, with the main components being aluminium oxide (Al2O3) 80%, zirconium oxide (ZrO2) 10%, silicon oxide (SiO2) 9%, as well as corundum, baddeleyite and cement. It was qualified in Voxeljet’s Material Certification Lab in Friedberg using a VX1000 AM machine.
During the Additive Manufacturing process, 50 µm-sized grains of Brightorb are applied to the build platform with layer thicknesses of 100 µm and selectively bonded with an inorganic binder. The inorganic binder is characterised by its environmental compatibility, as only water vapour is produced during moulding, thus improving working conditions in foundries.
To subsequently prepare the additively manufactured ceramic for the final application, the components are impregnated with a silica-based liquid and have to be fired in a sintering furnace for their final strength. Most of the unused powder can be reprocessed, recycled and fed back into the AM process.
“We have been noticing a growing demand for increasingly-complex component geometries among our customers for a long time,” stated Dr Ingo Ederer, CEO at Voxeljet. “The great advantage of the geometric freedom of 3D printing is that geometric adjustments can significantly optimise the efficiency and effectiveness of, for example, engines or turbine wheels.”
Ederer continued, “Together with AGC Ceramics, we have been able to optimise a VX1000 for ceramic powder in close cooperation, so that it is ideally suited for the challenging demands of metal casting. Both in terms of strength and surface quality.”
The resulting additively manufactured ceramics are suitable for use as cores for the investment casting process in order to reproduce complex and filigree cavities within castings. In this process, the filigree cores are combined with conventional wax patterns. These are coated with a ceramic slurry and burned out before casting, leaving a hollow ceramic mould in which the manufactured core is still inserted; molten metal is poured into the mould. After cooling, both the mould and the core are removed. This process makes it possible, for example, to integrate internal cooling channels in turbine blades, thus increasing turbine efficiency and reducing downtimes to a minimum.
“Brightorb is a high-performance ceramic that is extremely well suited for metal casting due to its high-chemical stability, heat resistance, thermal conductivity and low thermal expansion,” added Yukihiro Ushimaru, Additive Manufacturing Director from AGC Ceramics. “We were able to optimise the material set in such a way that the shrinkage factor of the printed components during the downstream sintering process at 1,400°C is less than 1%. This means that the components are also suitable for filigree core designs. Thanks to the high-fire resistance, it is possible to cast alloys with melting points beyond 1,600°C.”
“Overall, ceramics will continue to gain importance as a material in the future, and the same applies to 3D printing as a manufacturing technology. We are pleased to have embarked on this path together with Voxeljet and look forward to further close cooperation,” Yukihiro Ushimaru concluded.