Effect of different post-sintering temperatures on the microstructures and mechanical properties of a pre-sintered Co–Cr Alloy

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.