Sandvik Coromant Heat resistant super alloys - Manual (Page 53)

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3. Turning of cobalt-based materials
– medical
+ resistant to wear
(hard material 45-50 HRC).
+ can be cast into complex shapes.
+ high corrision resistance.
+ stronger than stainless steel.
– twice the weight of stainless steel.
– very brittle under impact loading.
The cobalt-based alloys in the medical
area are mainly of two types: CoCrMo and
CoNiCrMo.
CoCrMo alloys are used in applications
such as fixation screws, bone plates, shoul-
der, knee and hip replacement (coated or
uncoated, cemented or uncemented).
In this chapter of the application guide we
focus on the machining of hip joints in the
material group CoCrMo.
Chemical compositions of a few
Co-based alloys for implants
CoCr28Mo6 ASTM F75
Vitallium (Howmedica, Inc)
Haynes-Stellite 21 (Cabot Corp.)
Protasul-2 (Sulzer AG)
Micrograin-Zimaloy (Zimmer)
Co Cr Mo Mn Si Ni Fe C
58.9–69.5 27.0–30.0 5.0–7.0 Max 1.0 Max 1.0 Max 1.0 Max 0.75 Max 0.35
CoCrMo ASTM F799
Forged CoCrMo
Thermomechanical CoCrMo
FHS (Forged high strength)
Co Cr Mo Mn Si Ni Fe C N
58–59 26.0–30.0 5.0–7.0 Max 1.0 Max 1.0 Max 1.0 Max 1.5 Max 0.35 Max 0.25
Material properties