Cobalt-Cr Alloys

Cobalt-chrome or cobalt-chromium (CoCr) is a metal alloy of cobalt and chromium. Cobalt-chrome has a very high specific strength and is commonly used in gas turbines, dental implants, and orthopedic implants.
The common Co-Cr alloy production requires the extraction of cobalt and chromium from cobalt oxide and chromium oxide ores. Both of the ores need to go through reduction process to obtain pure metals. Chromium usually goes through aluminothermic reduction technique, and pure cobalt can be achieved through many different ways depending on the characteristics of the specific ore. Pure metals are then fused together under vacuum either by electric arc or by induction melting Due to the chemical reactivity of metals at high temperature, the process requires vacuum conditions or inert atmosphere to prevent oxygen uptake by the metal. ASTM F75, a Co-Cr-Mo alloy, is produced in an inert argon atmosphere by ejecting molten metal’s through a small nozzle that is immediately cooled produce fine powder of the alloy.
However, synthesis of Co-Cr alloy through the method mentioned above is very expensive and difficult. Recently, in 2010, scientists at the University of Cambridge have produced the alloy through a novel electrochemical, solid-state reduction technique known as the FFC-Cambridge Process which involves the reduction of an oxide precursor cathode in a molten chloride electrolyte.


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