The effect of solid solution treatment on the microstructure and properties of CoCrMo alloy

Cobalt-chromium-molybdenum (CoCrMo) alloys are widely used in orthopedic implants and aero-engine bearings due to their excellent mechanical properties and biocompatibility. This study aims to systematically investigate the influence of different solution treatment cooling methods on the microstructural evolution and key mechanical properties of this alloy to optimize its processing parameters. Existing research primarily focuses on solution temperature and time parameters, with relatively insufficient systematic investigation into how cooling methods affect the alloy's final microstructure and properties. This study innovatively employs multiple cooling methods (such as water quenching and air cooling) combined with varying solution times, utilizing a comprehensive approach including mechanical property testing, microstructural observation, and fracture analysis. The advantage of this method lies in its ability to clearly reveal how cooling rate regulates carbide dissolution, precipitation behavior, and grain size, thereby directly influencing the alloy's strengthening mechanisms. This provides a more comprehensive process basis for precisely controlling the comprehensive properties of CoCrMo alloys, holding significant engineering application value. Results indicate that regardless of the solution cooling method, the alloy's phase composition consists of a γ-Co matrix and M23C6 carbides. With increasing solution time (e.g., up to 1.5 hours), the primary M23C6 eutectic carbides and prior particle boundaries gradually dissolve, the M23C6 phase becomes refined and dispersed, leading to a significant improvement in alloy strength. However, excessively long times (e.g., beyond 1.5 hours) cause grain coarsening and a subsequent decrease in strength. The optimal solution treatment process for cast Co-Cr-Mo alloy, yielding the best comprehensive properties, is determined as 1230 °C for 1.5 hours (in conjunction with a specific cooling method). This study elucidates the key mechanism of the synergistic effect between cooling method and solution time, providing a crucial optimized processing window for obtaining high-performance CoCrMo alloys.