Growth of y-Co Phase on as-Cast Co-Cr-Mo Alloy via 1200 °C Solution Treatment: A Crystal Structure Investigation

摘要

Co-Cr-Mo alloys are widely used in the biomedical field especially for implant materials. The recommended Co-Cr-Mo alloy has to be a y-Co phase. This phase has a specific crystal structure characteristic, that is face-centered cubic (FCC). The solidification of Co-Cr-Mo is one way to form bulk Co-Cr-Mo alloy with consisting of y-Co phase. The process for solidifying Co-Cr-Mo alloy is casting process that will produce as-cast Co-Cr-Mo alloy. The random atomic arrangement has commonly happened in the as-cast product, and that always be a problem. This study presents a solution treatment method to solve this problem. The process of solution treatment is applying 1200 °C of heat to the sample in inert condition and holding it for about 60 min. The result of this study showed that there was a transformation from random (disordered) to a more ordered structure after the homogenization process. The solution treatment method also can produce y-Co phase (FCC) followed by the hexagonal structure as a minor phase. The best-ordered unit-cell of FCC (y-Co phase) occurred via homogenization-hot rolling-cold water quenching-solution treatment route. However, the highest y-Co phase (FCC) and the lowest hexagonal structure composition occurred via homogenization-hot rolling-water quenching-solution treatment route. From this study, we can suggest that solution treatment at 1200 °C can improve the composition of y-Co phase on as-cast Co-Cr-Mo alloy.