Innovative Si3N4 feedstock: from slurry development for DLP technology to 3D-printing of a prototype component for high-performance applications

Additive manufacturing (AM) technologies are currently attracting considerable interest due to their sustainability and versatility, and many studies are being conducted to use them for all classes of materials. In particular, AM is also spreading to ceramic materials, as an innovative net-shape forming technique, but few feedstocks are currently available for printing ceramic components.The present study is aimed at developing feedstocks, i.e. slurries, for the AM technology denominated Digital Light Processing (DLP), which involves the layer-by-layer polymerisation of a photosensitive liquid resin, loaded with ceramic powders to obtain a ceramic component after sintering.In this work, feedstocks based on silicon nitride (Si3N4) powders were developed. The objective was to demonstrate the feasibility of the entire ceramic AM process, from the development of the ceramic feedstock and its printability via DLP, to the prototype production. This process involved the materials selection: functionalized monomers, dispersants, photoinitiators, and ceramic powders. Through ongoing rheological tests, their percentages were finetuned with the goal of achieving low viscosity and high solids content. The DLP feedstock setup phase was followed by printability tests of standard geometries, which let to identify the most suitable printing parameters for the developed material. The printed specimens were then subjected to debinding and sintering thermal cycles, to remove the resin and obtain the final ceramic samples. Both cycles included preliminary tests. A characterization campaign was carried out on sintered samples obtained via DLP printing. Finally, a micro-gas-turbine impeller was designed and printed as prototype of ceramic component potentially operating in high-performance environments, to validate the slurry printability and the entire process.