Previous studies have shown it is possible to initiate selective laser flash sintering (SLFS) by applying an electric field while scanning a laser. Chemical bonding between particles results without the need for polymer binders and at much lower temperatures and faster times than with traditional laser sintering. However, these studies were not successful in consistently producing crack-free parts using direct-current electric fields. The purpose of this study is to study the use of alternating current (AC) electric fields to produce crack-free parts.
AC fields were used and the effects of laser power and field frequency on the initiation of SLFS were studied using single line scans.
It was found that, for the scan conditions studied, a processing window existed with AC fields where SLFS was initiated at temperatures as low as 320 °C and cracking was not visible until temperatures reached 430 °C. Experiments also showed that pairs of scan lines produced regions without cracking using open-loop control to maintain an approximately constant temperature from line-to-line.
The research focused on single-layer scanning. To produce 3D parts, it must be expanded to larger scanned hatches and multiple layers.
Implications of these results toward the binder-free additive manufacturing of multi-layer ceramic parts and potential methods for expanding the processing window are discussed.
This paper demonstrates that it is possible to bond particles by interparticle neck formation while producing crack-free scanned regions using open-loop control. This is a key step toward developing SLFS for ceramics.
