Influences of energy density on microstructure and consolidation of selective laser melted bismuth telluride thermoelectric powder

Selective laser melting is a well-established additive manufacturing technique for metals and ceramics, and there is significant interest in expanding the manufacturing capability of this technique by enabling processing of more materials. Notably, selective laser melting has not been demonstrated on semiconducting materials which are significant for energy conversion technologies. Thermoelectric materials are semiconductors that can convert heat into electrical power. The traditional thermoelectric manufacturing process involves many assembly and machining steps which lead to material losses, added time and cost, and performance degradation. Utilizing selective laser melting in the manufacturing of thermoelectric modules can minimize assembly steps and eliminate machining processes. In this study, a standard bismuth telluride thermoelectric powder was processed for the first time in a commercial Prox™ 100 selective laser melting system under different energy densities. The surfaces of Bi2Te3 specimens were successfully melted under all processing conditions, and the entire thickness of specimens processed at higher laser power inputs was mostly melted. The increase in laser power also reduced the presence of porosities on the surface of the specimens. However, cross-sectional examination showed that internal pores were present within the molten region and at the interface between the molten region and the unmelted powder under all investigated laser power inputs. The consistency of these results with early results for select laser melting of metals demonstrates the promise for expanding the materials processing capabilities of this additive manufacturing technique.