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Cobalt Alloys

Cobalt is also used to make alloys for jet engines and gas turbines, magnetic steels and some types of stainless steels. Cobalt-60, a radioactive isotope of cobalt, is an important source of gamma rays and is used to treat some forms of cancer and as a medical tracer.

Cobalt 1

ECoCr-C & ERCoCr-C

ECoCr-C & ERCoCr-C have a higher percentage (approximately 19%) of carbides than deposits made using either ECoCr-A (Cobalt 6) or ECoCr-B (Cobalt 12). In fact, the composition, is such that primary hypereutectic carbides are found in the microstructure. This characteristic gives the alloy higher wear resistance accompanied by reductions in the impact and corrosion resistance. The higher hardness also means a greater tendency may be minimized by closely monitoring preheating, interpass temperature, and postheating techniques.

Cobalt 6

ECoCr-A & ERCoCr-A

ECoCr-A & ERCoCr-A electrodes are characterized by a hypoeutectic structure, consisting of a network of about 13% eutectic chromium carbides distributed in a cobalt-chromium-tungsten solid solution matrix. The result is a material with a combination of overall resistance to low stress abrasive wear, with the necessary toughness to resist some degree of impact. Cobalt alloys also are inherently good for resisting metal-to-metal wear, particularly in high load situations that are prone to galling. The high-alloy content of the matrix also affords excellent resistance to corrosion, oxidation, and elevated temperature retention of hot hardness up to a maximum of 1200°F (650°C). These alloys are not subject to allotropic transformation and therefore do not lose their properties if the base metal is subsequently heat treated.

Cobalt 12

ECoCr-B & ERCoCr-B

ECoCr-B & ERCoCr-B electrodes and rods are similar in composition to deposits made using ECoCr-A (Cobalt 6) electrodes and rods, except for a slightly higher percentage (approximately 16%) of carbides. The alloy also has a slightly higher hardness and better abrasive and metal-to-metal wear resistance. Impact and corrosion resistance are lowered slightly. Deposits can be machined with carbide tools.

Cobalt 21

ECoCr-E, ERCoCr-E & AMS 5385

ECoCr-E & ERCoCr-E electrodes have very good strength and ductility in temperatures up to 1600°F (871°C). Deposits are resistant to thermal shock, oxidizing, and reducing atmospheres. Early applications of these types of alloys were found in jet engine components such as turbine blades and vanes. The deposit is a solid solution straightened alloy with a relatively low weight-percent carbide phase in the microstructure. Hence, the alloy is very tough and will work harden. Deposits possess excellent self-mated galling resistance and also are very resistant to cavitation erosion.