Cobalt-Chrome Alloy S-816-AC vs S-816-ST
Cobalt-Chrome Alloy · S-816 temper comparison
S-816-AC and S-816-ST are two conditions of the same cobalt-chrome alloy grade, S-816: AC (spheroidize annealed) versus ST (solution annealed). The chemistry is identical, so every difference below comes from the condition. S-816-AC is the stronger of the two: yield strength 430 MPa (62.4 ksi) against 345 MPa (50 ksi) for S-816-ST, about 25% more. In exchange, S-816-ST is the more ductile: elongation 38% versus 9% for S-816-AC, and S-816-AC is harder (285 HB vs 220 HB). On the shop floor, S-816-ST welds better (fair vs poor).
S-816-ACChoose it when strength drives the design.
S-816-STChoose it when the part is bent, formed or impact-loaded, or when it will be welded.
S-816-AC vs S-816-ST: 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
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 77 GPa11.2 Msi · Bulk Modulus 172 GPa24.9 Msi · Poisson's Ratio 0.3
Physical
Density and transition temperatures.
Same in both: Density 8.68 g/cm³0.31 lb/in³ · Melting Point (Solidus) 1,330°C2,426 °F · Liquidus Temperature 1,400°C2,552 °F
Thermal
How each material carries heat and how hot it can run.
Same in both: Thermal Conductivity 12.5 W/m·K7.2 BTU/hr·ft·°F · Specific Heat Capacity 420 J/kg·K0.1 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 13.9 µm/m·K7.7 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Max Service Temperature (continuous) 870°C1,598 °F · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 1.9 % IACS · Electrical Resistivity 9.1×10⁻⁷ Ω·m35.8 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.15 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Castability 68 / 100 · Brazeability / Solderability 55 / 100 · Polishability 65 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 190 MJ/kg81,685 BTU/lb · Embodied Carbon (primary production) 13 kg CO₂/kg · Embodied Water 340 L/kg40.7 gal/lb · Typical Recycled Content 30%
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.
S-816-AC vs S-816-ST — frequently asked
Is S-816-AC stronger than S-816-ST?
Yes. S-816-AC has a typical yield strength of 430 MPa (62.4 ksi) against 345 MPa (50 ksi) for S-816-ST — about 25% more. Tensile strength is 745 MPa (108 ksi) vs 830 MPa (120 ksi).
Which condition does FabDigit quote by default, AC or ST?
STA is the default S-816 condition in the FabDigit quote flow (neither AC nor ST). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, S-816-AC or S-816-ST?
S-816-ST. Its machinability rates poor (18/100) against not recommended (12/100) for S-816-AC; for welding the order is S-816-ST first (fair, 35/100) then S-816-AC (poor, 22/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in S-816-AC and S-816-ST 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.