Co21 Rod

Co21 was developed as a corrosion resistant CoCr alloy, and rapidly found application as a biocompatible hip implant and denture alloy. Many of the alloys currently used in medical applications are variants of the original Co21 composition. It was also one of the first heat-resistant alloys trialled for use in jet engines.

Co21 consists of a CoCrMo alloy matrix containing dispersed hard carbides which strengthen the alloy and increase its hardness, but also decrease the ductility. The type, shape, size, and distribution of the carbides is strongly influenced by the processing history of the alloy, and for this reason the mechanical properties of Co21 are very dependent upon the manufacturing route and any subsequent heat treatments.

Due to the low volume fraction of carbides, the Co-based alloy matrix dominates the wear and corrosion properties. Co21 has excellent cavitation, galling and metal-to-metal sliding wear resistance, but is not recommended for severe hard particle abrasion. The surface can work harden considerably during wear or even during machining, and the use of correct machining tools and techniques is important to achieve optimal results.

Equivalent: Stellite 21, Bishilite No.21

Standard: AWS A5.21 ERCoCr-E