Debinding and sintering optimization of stereolithography based silicon nitride parts for attaining centimetric wall-thickness shapes

Stereolithography of UV-curable ceramic suspensions is an additive manufacturing technique with high precision and great resolution to fabricate complex ceramic parts. While it widens the possibilities of applications, one of the drawback of this method is the low wall-thickness of the parts. The polymers forming the network structure upon cross-linking undergo pyrolysis in a step called debinding. During debinding, the gaseous compounds going through evacuation channels create internal pressures, often resulting in crack formation. So far, the critical wall-thickness where crackfree parts are obtained is located around 4 millimeters for silicon nitride. This paper reports the successful debinding of silicon nitride parts obtained by stereolithography. Thanks to an optimization of the debinding relying on TGA analysis, defectless parts with a wall-thickness of up to 11 mm were obtained, yielding parts of 9 mm after sintering. The mechanical properties were measured, showing values equivalent to silicon nitride obtained through conventional methods.