Microwave post-processed silicon carbide samples 3D printed using direct ink writing technique

Abstract

Direct ink writing (DIW) 3D-printed ceramic parts post-processing requires binder debinding and part densification during sintering. The use of conventional heating sources during the sintering of DIW 3D printed ceramics consumes significant time due to the slow conduction of heat inside the ceramic parts. Microwave energy-based post-processing can be a suitable alternative for rapid and more uniform heating of ceramic materials such as SiC, which couples microwave energy. In the present work, SiC-based ink (flow behaviour index 0.6) was prepared to build 3D-printed SiC parts using the DIW process; subsequently, parts were post-processed using microwave energy. The effects of different debinding temperatures (900 °C, 950 °C, and 1000 °C) and heating rates (15 °C/min, 20 °C/min, and 25 °C/min) were analysed on the properties of SiC samples. The microstructural characterization revealed the formation of an oxide layer on the edges of SiC particles, which results in the formation of necking between SiC particles. In contrast, an increase in the heating rate impedes the growth of the oxide layer. The phase analysis confirms the presence of SiO2 and the transformation of β-SiC to α-SiC. Higher debinding temperature and lower heating rate favour an increase in oxide layer formation; consequently, the flexural strength of SiC samples increases. The SiC samples fabricated at 1000 °C debinding temperature and a heating rate of 15 °C/min exhibit the highest flexural strength compared to SiC samples developed at higher heating rates due to poor bonding among the SiC particles.