Reaction-bonded carbides were manufactured using a combination of robocasting and liquid silicon infiltration. Robocasting, an additive manufacturing process, uses highly filled ceramic pastes, which were printed layer-by-layer, to generate complex structures. By varying the paste composition, different porous preforms can be generated which were subsequently infiltrated with liquid silicon, resulting in reaction-bonded silicon carbide (RBSC), reaction-bonded boron carbide (RBBC), and a reaction-bonded silicon and boron carbide composite (RBSBC). The influence of the shaping method on the microstructure and properties was investigated and no significant difference from traditionally fabricated samples was found.
Moreover, the feasibility of producing multi-material samples was shown in this work. Multi-material printing offers the possibility to combine various materials and simultaneously their properties. Layered structures with varying layer heights consisting of RBSC and RBBC or RBSC and RBSBC were realized and studied. Whereas crack formation in the RBBC layer was observed in the RBSC-RBBC composites after infiltration with liquid silicon, crack-free samples were obtained when exchanging RBBC with RBSBC. The crack formation is due to residual stresses occurring in the respective layers. These stresses were analyzed on microscopic as well as macroscopic levels. Using Raman spectroscopy and investigations on crack patterns obtained by Vickers indentation the stresses could be calculated and could be used to explain crack formation or crack inhibition. In addition to layered structures, core-shell structures were also realized and investigated. The effect of rheology on the printability of the structures was studied and the influence of residual stresses on crack formation was analyzed.