Impact of Porcelain Firing Cycling on the Microstructure and Mechanical Properties of Selective Laser-Melted Co-Cr-Mo-W Dental Alloys

To adhere to esthetic standards, porcelain-fused-to-metal (PFM) restorations are commonly fabricated utilizing porcelain firing cycling (PFC) to bond ceramics onto metal substrates. However, the impact of PFC on the microstructure and mechanical properties of selective laser-melted (SLM) Co-Cr-Mo-W dental metal-ceramic alloys remains unclear. In this study, the influence of PFC on the microstructure and mechanical properties of different states of SLM Co-Cr-Mo-W dental alloys (As-SLM, hardening heat-treated, and softening heat-treated) was investigated. These findings reveal that PFC treatment significantly impacts mechanical properties, with varying effects on different alloy states. In As-SLM samples, it enhances strength but reduces elongation due to the emergence of ε-Co and Laves phases. In hardening heat-treated (HT) samples, PFC reduces strength but enhances elongation by replacing brittle ε-Co with more ductile γ-Co. In softening HT samples, PFC increases strength and reduces elongation, primarily due to the supersaturated microstructure leading to the precipitation of dispersed Laves phases within the grains. This investigation provides insights to optimize SLM Co-Cr-Mo-W alloy restorations for dental applications.