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.

Keywords

• cobalt–chromium alloy
• powder metallurgy
• sintering
• microstructure
• mechanical properties