Researchers at the NUST MISIS have enhanced the processing method for a cobalt-chromium-molybdenum alloy used in hip joint implants, pins, plates, and other biomedical products. This approach improves the material’s strength characteristics while maintaining a stable level of plasticity.
Cobalt alloys are in high demand for producing heavily loaded orthopedic implants due to their high strength, biocompatibility, wear resistance, and corrosion resistance. To enhance mechanical properties and refine the cast structure, manufacturers often resort to hot forging. However, maintaining a narrow temperature deformation range and ensuring the required dimensional specifications complicates the process significantly. To simplify production efforts, NUST MISIS researchers proposed the additional use of radial-shear rolling to obtain rods with freely selectable sizes and improved characteristics.
“The proposed method combines preliminary isothermal forging with subsequent radial-shear rolling, resulting in a significant improvement in microstructure. The enhancement of strength characteristics without loss of plasticity is achieved through effective deformation processing and the formation of a gradient two-phase structure in the alloy. This combination of properties is particularly important for products operating under cyclic loads during prolonged use,” said Yuri Gamin, Candidate of Sciences, Associate Professor at the Department of Metal Forming at NUST MISIS.
In the first phase of the work, the research team explored the possibility of using isothermal forging for processing the initial ingot, which allowed for preliminary deformation within the required temperature range while refining the structure without forming embrittling intermetallic phases. In the second phase, radial-shear rolling of forged blanks was conducted on pilot-industrial equipment at the Research and Production Center of Metal Processing with Pressure at NUST MISIS, resulting in a gradient duplex structure in the rods. Detailed results have been published in the scientific journal Metals and Materials International (Q1).
This work was supported by the Russian Science Foundation (project No. 23—19—00477).
