Reusing the Co–Cr–Mo support structures of selective laser melted parts: Evaluation of mechanical properties and microstructures

Abstract

The disposal of the support structures used in the selective laser melting (SLM) process in metal additive manufacturing leads to material waste, which negatively affects sustainability and increases the overall process cost. In addition, it increases the need to mine new metals, which has harmful impacts on the environment and energy resources. This study aims to test the mechanical properties of the reused Co–Cr–Mo support structures of SLM parts using the dental casting technique and compare them with those of conventional Co–Cr–Mo alloy ingots. Heat-treated and non-heat-treated SLM support structures and conventional Co–Cr–Mo alloy ingots were used as raw materials to fabricate 21 cast dumbbell-shaped specimens. The ultimate tensile strength (UTS), elongation, 0.2% offset yield strength (0.2 YS), and Vickers hardness were evaluated. Their microstructures were investigated using confocal laser scanning microscopy, scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, and electron backscattering diffraction. One-way ANOVA and Tukey's multiple comparison tests were used for statistical analysis (α = 0.05). The results showed no significant difference in the UTS, 0.2% YS, and hardness among all groups. The elongation of the conventional group was significantly higher than that of the non-heat-treated group, while it was not significantly different among the remaining groups. The mechanical properties of all groups satisfied ISO 22674; thus, from the mechanical viewpoint, SLM support structures can be reused for the fabrication of removable and fixed dental prostheses, contributing to minimizing the material waste and the need for new metal extraction.