Open loop control of selective laser flash sintering conducted with AC electric fields

Purpose 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. Design/methodology/approach AC fields were used and the effects of laser power and field frequency on the initiation of SLFS were studied using single line scans. Findings 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. Research limitations/implications The research focused on single-layer scanning. To produce 3D parts, it must be expanded to larger scanned hatches and multiple layers. Practical implications 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. Originality/value 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.