S81921 Stainless Steel vs. R30021 Cobalt
S81921 stainless steel belongs to the iron alloys classification, while R30021 cobalt belongs to the cobalt alloys. They have a modest 27% of their average alloy composition in common, which, by itself, doesn't mean much. There are 28 material properties with values for both materials. Properties with values for just one material (7, in this case) are not shown.
For each property being compared, the top bar is S81921 stainless steel and the bottom bar is R30021 cobalt.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 200 | |
| 220 |
| Elongation at Break, % | 29 | |
| 9.0 |
| Fatigue Strength, MPa | 370 | |
| 250 |
| Poisson's Ratio | 0.28 | |
| 0.29 |
| Rockwell C Hardness | 27 | |
| 32 |
| Shear Modulus, GPa | 79 | |
| 86 |
| Tensile Strength: Ultimate (UTS), MPa | 710 | |
| 700 |
| Tensile Strength: Yield (Proof), MPa | 500 | |
| 500 |
Thermal Properties
| Latent Heat of Fusion, J/g | 290 | |
| 330 |
| Melting Completion (Liquidus), °C | 1430 | |
| 1350 |
| Melting Onset (Solidus), °C | 1390 | |
| 1190 |
| Specific Heat Capacity, J/kg-K | 480 | |
| 450 |
| Thermal Conductivity, W/m-K | 15 | |
| 15 |
| Thermal Expansion, µm/m-K | 13 | |
| 11 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 2.2 | |
| 1.9 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 2.5 | |
| 2.1 |
Otherwise Unclassified Properties
| Density, g/cm3 | 7.7 | |
| 8.4 |
| Embodied Carbon, kg CO2/kg material | 2.9 | |
| 8.0 |
| Embodied Energy, MJ/kg | 41 | |
| 110 |
| Embodied Water, L/kg | 150 | |
| 520 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 180 | |
| 57 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 630 | |
| 570 |
| Stiffness to Weight: Axial, points | 14 | |
| 15 |
| Stiffness to Weight: Bending, points | 25 | |
| 24 |
| Strength to Weight: Axial, points | 25 | |
| 23 |
| Strength to Weight: Bending, points | 23 | |
| 21 |
| Thermal Diffusivity, mm2/s | 4.0 | |
| 3.8 |
| Thermal Shock Resistance, points | 20 | |
| 21 |
Alloy Composition
| Carbon (C), % | 0 to 0.030 | |
| 0.2 to 0.35 |
| Chromium (Cr), % | 19 to 22 | |
| 26 to 29 |
| Cobalt (Co), % | 0 | |
| 61.7 to 67.3 |
| Iron (Fe), % | 66.7 to 75.9 | |
| 0 to 3.0 |
| Manganese (Mn), % | 2.0 to 4.0 | |
| 0 |
| Molybdenum (Mo), % | 1.0 to 2.0 | |
| 4.5 to 6.0 |
| Nickel (Ni), % | 2.0 to 4.0 | |
| 2.0 to 3.0 |
| Nitrogen (N), % | 0.14 to 0.2 | |
| 0 |
| Phosphorus (P), % | 0 to 0.040 | |
| 0 |
| Silicon (Si), % | 0 to 1.0 | |
| 0 to 1.5 |
| Sulfur (S), % | 0 to 0.030 | |
| 0 |