Effect of Cooling Rate on Structural, Corrosion, and Mechanical Properties of Cobalt–Chromium–Molybdenum Dental Alloys

The medical field, particularly dentistry, frequently employs cobalt-chromium-molybdenum dental alloys for their biocompatibility, strength, corrosion resistance, and wear resistance. This study aimed to assess the impact of the cooling rate during alloy casting on the structural properties, corrosion resistance, and mechanical properties. Three samples were cast using different types of mold materials (dental plaster, alumina, and graphite) by precision centrifugal casting. The samples were characterized using optical microscopy, X-ray diffraction, elemental analysis, corrosion test, and mechanical tests, which included the Macro Vickers hardness test and four-point bending test. The results revealed that the dendritic branch spacing of the plaster mold sample, which was 17 μm, decreased to 3 μm in the graphite mold sample. Increasing the cooling rate through graphite molding resulted in an insignificant phase transformation that occurred during the α-FCC transformation into a hexagonal crystalline structure (ε phase). Additionally, specimens with a high density of small-sized grains in their microstructure exhibit lower corrosion resistance, higher corrosion rates, and higher hardness. The plaster mold yielded the highest bending strength, whereas the sample cast in graphite exhibited the lowest bending strength.