Cobalt alloys

Classified by use, cobalt-based alloys can be divided into cobalt-based wear-resistant alloys, cobalt-based high-temperature alloys, and cobalt-based wear-resistant and aqueous solution corrosion alloys.

Under normal operating conditions, in fact, they are both wear-resistant, high-temperature resistant, or wear-resistant and corrosion-resistant. Some operating conditions may also require high-temperature, wear-resistant, and corrosion-resistant materials at the same time. Under certain circumstances, the more it can reflect the advantages of cobalt-based alloys.

The typical grades of cobalt-based high temperature alloys are: Haynes 188, Haynes 25 (L-605), Alloy S-816, UMCo-50, MP-159, FSX-414, X-40, Stellite, etc.
Chinese grades are: GH5188(GH188 ), GH159, GH605, K640, DZ40M and so on. Different from other superalloys, cobalt-based superalloys are not strengthened by an ordered precipitation phase firmly bonded to the matrix, but are composed of an austenite fcc matrix that has been solid solution strengthened and a small amount of carbides distributed in the matrix.
Casting cobalt-based superalloys relies heavily on carbide strengthening. Pure cobalt crystals have a hexagonal close-packed (hcp) crystal structure below 417°C and transform to fcc at higher temperatures. To avoid this transformation during the use of cobalt-based superalloys, practically all cobalt-based alloys are alloyed with nickel to stabilize the structure from room temperature to the melting point.
Cobalt-based alloys have a flat fracture stress-temperature relationship, but they show better thermal corrosion resistance than other high alloys above 1000°C. This may be due to the higher chromium content of the alloy, which is the most important part of this type of alloy.