Therefore, if we design a rotor for a gas turbine merely on the basis of yield strength during a tensile test, it will fail when it is in service, because the blades will heat up and either stretch excessively and contact the housing or break after a period of time. Nickel is one of the metals that has high resistance to corrosion. When used with chromium , it is resistant to high temperature oxidation and corrosion. When combined with manganese it is resistant to oxidation and reduction at elevated temperatures. Nickel with cobalt provides high heat resistance which makes it useful in chemical industry.
Cobalt is a high performance material.
It achieves its strength through solid solution strengthening and precipitation hardening. Cobalt based alloys are combined with chromium, molybdenum, or tungsten all of which have melting points between 2200 and 2500 F range. Cobalt based materials have low machinability because of rapid work hardening that takes place at elevated temperatures and the abrasive particles that exist in the lattice and grain boundaries. Titanium and its alloys are relatively new engineering materials that possess an extraordinary combination of properties. The alloys are highly ductile and easily machines.