Solubility of cobalt in iron α is up to 75% whilein the iron is γ unlimited. Cobalt is the only one alloying
additive that increases the critical cooling rate of steel and accelerates pearlitic transformation - reduces hardenability.
Since cobalt has an negative effect on hardenability, affects the hardening less than other elements, has a tendency
to graphitization and is a very expensive component, it is not used as an alloying addition in alloy steels. The presence
of this element in the steel improves its durability and hardness at higher temperatures, reduces the fall in hardness of
austenite and ferrite under the influence of temperature increase, and therefore is used as a supplement to some grades
of high speed steel, tool steel of some grades of hot work, is also a component of creep resistant alloys and steels and
alloys with special magnetic properties.
