Towards Functionally Graded Sand Molds for Metal Casting: Engineering Thermo-mechanical Properties Using 3D Sand Printing

Growing applications of additive manufacturing (AM) have now been adopted for metal castings via indirect hybrid AM, i.e., 3D sand printing (3DSP). A comprehensive study on the thermo-physical properties of 3DSP molds based on 3DSP processing conditions and their effects on materials and mechanical properties of resulting aluminum castings is presented. The effect of furan binder content (i.e., 1–3%) on as-printed 3DSP molds is evaluated to determine changes in dimensional accuracy, density (helium pycnometry), actual binder content (loss on ignition) and mechanical strength (three-point bending and tensile testing) and thermal properties (transient plane source technique and casting runs). Pore network characterization via mercury intrusion porosimetry does not reveal any significant differences in the morphology of pore structures due to varying binder concentrations. However, bulk permeability is reduced with increasing binder content. Thermal analysis shows a reduction in conductivity and heat capacity due to binder degradation. Findings from this study will enable the optimum selection of binder content for functional grading of 3DSP molds/cores for adequate degassing and mechanical strength, which is ready for adoption by both foundries and 3DSP service providers.