Effect of Different Post-Sintering Temperatures on the Microstructures and Mechanical Properties of a Pre-Sintered Co–Cr Alloy

Abstract

Although a cobalt–chromium (Co–Cr) blank in a pre-sintered state has been developed, there are few data on the optimal temperature for the alloy in terms of the desired mechanical properties. A metal block (Soft Metal, LHK, Chilgok, Korea) was milled to produce either disc-shaped or dumbbell-shaped specimens. All the milled specimens were post-sintered in a furnace at 1250, 1350 or 1450 °C. The microstructures, shrinkage and density of the three different alloys were investigated using the disc-shaped specimens. The mechanical properties were investigated with a tensile test according to ISO 22674 (n = 6). The number and size of the pores in the alloys decreased with increased temperature. The shrinkage and density of the alloys increased with temperature. In the 1250 °C alloy, the formation of the ε (hexagonal close-packed) phase was more predominant than that of the γ (face-centered cubic) phase. The 1350 °C and 1450 °C alloys showed γ phase formation more predominantly. Carbide formation was increased along with temperature. The 1450 °C group showed the largest grain size among the three groups. In general, the 1350 °C group exhibited mechanical properties superior to the 1250 °C and 1450 °C groups. These findings suggest that 1350 °C was the most optimal post-sintering temperature for the pre-sintered blank.

Mechanical Properties of Dental Alloys According to Manufacturing Process

“…The 3D printed specimen has a disadvantage in that the manufacturing cost is not economical and has a brittle property. However, this method has a fast production speed, less material waste, and a significantly lower incidence of porosity [ 6 , 7 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

Comparative clinical study of the marginal discrepancy of fixed dental prosthesis fabricated by the milling-sintering method using a presintered alloy

“…The effect of sintering temperatures on the mechanical properties of a presintered Co-Cr alloy was examined, and the result indicated that over-sintering, about 1350℃, is better than under-sintering in terms of strength. It also showed that the number and size of the pores in the microstructure were largely related to the sintering temperature 26…”

New generation CAD-CAM materials for implant-supported definitive frameworks fabricated by using subtractive technologies

“…A presintered soft block can be milled by dry machining with low contamination risk, which is an easier process than sintered Co-Cr milling [ 19 ]. The milled framework should be sintered in an argon atmosphere sintering oven at 1250-1400°C for 1 hour or 2 hours [ 20 , 21 ]. While there is no contraction shrinkage of a fully-sintered alloy used for hard milling, the shrinkage rate is 10-11% for soft-milled alloys after sintering [ 14 , 22 , 23 ].…”

“…While there is no contraction shrinkage of a fully-sintered alloy used for hard milling, the shrinkage rate is 10-11% for soft-milled alloys after sintering [ 14 , 22 , 23 ]. The post-sintering after milling could affect the mechanical strength of soft-milled alloy [ 21 ], and 1350°C was reported to be the most suitable temperature [ 20 , 21 ].…”