This study evaluated the mechanical properties and microstructure, in various metallurgical conditions, of an alloy meeting the requirements of the ASTM Specification for Cast Cobalt-Chromium-Molybdenum Alloy for Surgical Implant Applications (F 75–82). Standard mechanical property analyses such as tensile and yield strength, percentage of elongation, and rotating-beam fatigue tests were performed. The materials were tested in the as-cast, as-cast plus solution-annealed, as-cast plus hot-isostatic-pressed (HIP) plus solution-annealed, and as-cast plus HIP plus sintered conditions. Chemical analyses of the test specimens were reviewed to determine the extent of the correlation between mechanical properties and certain elements within the alloy, as has been suggested by other authors.
No effect on ultimate tensile strength was observed with a reduction of carbon content from 0.30 to 0.24%, but a reduction of the yield strength and a corresponding increase in ductility were observed. The as-sintered surface appeared to reduce the fatigue properties of the test specimens. A direct correlation between the fatigue properties, static mechanical properties, and microstructure was not established.