Cobalt alloys
Stellite 21
Route-sensitive cobalt alloy; use the designation required for the casting or consumable.
Identity / state reference
What distinguishes this material
A lower-carbon Co-Cr-Mo direction for galling/cavitation service; the producer explicitly excludes severe hard-particle abrasion as a preferred use.
- Designation in this reference
- Co-Cr-Mo alloy; product-route-specific specification
- Forms covered by the sources
- Cast component
- Hardfacing / deposited layer
- States to distinguish or confirm
- As cast or specified heat treatment
- As deposited; work-hardened surface distinguished
- Temperature and exposure
- A service-temperature statement is not an allowable stress or a guarantee at temperature. Use the specified product condition and exposure duration.
Other search names in these sources
Stellite 21 · R30021
Read the scope above: a source’s related product name is not a blanket interchangeability statement.
Property evidence for a stated condition
No condition-specific numerical table is reproduced here
The linked sources establish the identity and the stated product/state scope. Obtain the row for your actual form, section, treatment and test conditions before adopting strength, hardness or a thermal limit.
Resolve these conditions next
- Is galling/cavitation or hard-particle abrasion the main failure mode?
- What manufacturing route and heat treatment define the final surface?
For machining, take the exact grade, supplied condition and measured hardness where applicable into the tool maker’s application data. A generic material-family speed is not a substitute for an operation and tool-specific recommendation.
Sources and what they establish
Reviewed 23 October 2026. A source’s publication date and the review date are different. The scope below identifies the fields checked.
Kennametal Stellite: cobalt-based alloys
Stellite 6 and 21 identities and route-sensitive behavior; listed UNS numbers vary with product route.
Kennametal Stellite: cobalt-based alloys ↗Source identity, a named product example and a supplied-batch certificate are different evidence. Cross-standard similarity does not approve substitution.
Corrections from the previous article
- The old single 28–38 HRC range hides manufacturing route, heat treatment and work hardening.
- Remove generic machinability and speed values with no identified process evidence.
Other references in Cobalt alloys
Related references, not equivalent substitutes.