Direct ink writing of water-based C-SiC pastes for the manufacturing of SiSiC components

As a feasibility study, a direct ink writing process using a conventional FDM-printer and colloidal C-SiC pastes was developed. The pastes have a low content of organic additives, which enables the omission of a pyrolysis step, i.e. the green parts can undergo the liquid silicon infiltration process directly after drying. The rheological behavior of the pastes was investigated regarding their viscosity, thixotropy and yield point. By analyzing important effects of 3D-printing, such as bridging and the possibility to print overhangs, the printability was determined. The near-net shape ability of the process was studied by comparing the dimensions after each processing step. The microstructure of the samples showed no detectable microstructural anomalies in this interface area. The phase analysis of the samples showed no residual carbon in the SiSiC parts. Printed SiSiC parts reached flexural strengths of 190 MPa, a hardness of 15.7 GPa and a Young's Modulus of 246 GPa.