Optimizing the corrosion fatigue properties of Co-Cr-Mo Hip joints

Because of their affordability and their adaptability to different designs, cast Co-Cr-Mo alloys are the materials most used for hip joint endoprostheses. These alloys combine excellent biocompatibility with a high corrosion resistance. Most hip joint endoprostheses are manufactured by conventional casting. The microstructural defects caused by this casting method lead to premature fractures. Aseptic loosening of endoprostheses also contributes to fracture. This article shows that using unidirectional solidification prolongs the mean value of fatigue life by at least six times over conventional casting; comparing the lowest values, the fatigue life is more than ten times higher. The comparison is made for two different kinds of solidified tension-compression specimens without any heat treatment to study only the influence of the solidification process. It should also be noted, however, that heat treatment adapted to microstructural parameters can elevate fatigue life. 7 refs., 1 tab., 6 figs. including photo-micrographs.