Cobalt-Chrome Alloy Stellite 21 vs Ultimet
Cobalt-Chrome Alloy · grade comparison
Cobalt-Chrome Alloy Stellite 21 and Ultimet are both cobalt-chrome alloy grades. Ultimet is the stronger of the two: tensile strength 1,000 MPa (145 ksi) against 710 MPa (103 ksi) for Stellite 21, about 41% more. Ultimet is the more ductile: elongation 39% versus 9% for Stellite 21, and Stellite 21 is harder (300 HB vs 277 HB). Stellite 21 is stiffer (248 GPa vs 224 GPa) and Ultimet runs hotter in service (900°C vs 760°C continuous). On the shop floor, Ultimet welds better (very good vs good) and Ultimet sits in a lower cost tier (high, $$$$) than Stellite 21 (specialty, $$$$$).
UltimetChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
Stellite 21 vs Ultimet: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all cobalt-chrome alloy grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all cobalt-chrome alloy grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Bulk Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Poisson's Ratio 0.3
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Liquidus Temperature
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Same in both: Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Same in both: Electrical Conductivity 2 % IACS
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Castability
Brazeability / Solderability
Same in both: Machinability Rating (AISI 1212 = 100 %) 10% · Polishability 85 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every cobalt-chrome alloy grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Stellite 21 | Ultimet |
|---|---|---|
| Default condition | As Cast | — |
| Relative cost | $$$$$ Specialty | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Stellite 21 vs Ultimet — frequently asked
Is Ultimet stronger than Stellite 21?
Yes. Ultimet has a typical tensile strength of 1,000 MPa (145 ksi) against 710 MPa (103 ksi) for Stellite 21 — about 41% more.
Which is cheaper, Stellite 21 or Ultimet?
Ultimet is the lower-cost material: it sits in the high tier ($$$$) while Stellite 21 is specialty ($$$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which welds better, Stellite 21 or Ultimet?
Ultimet. Its weldability rates very good (75/100) against good (55/100) for Stellite 21.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Stellite 21 and Ultimet side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.