S21904 Stainless Steel vs. R30021 Cobalt
S21904 stainless steel belongs to the iron alloys classification, while R30021 cobalt belongs to the cobalt alloys. They have a modest 25% of their average alloy composition in common, which, by itself, doesn't mean much. There are 27 material properties with values for both materials. Properties with values for just one material (8, in this case) are not shown.
For each property being compared, the top bar is S21904 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, % | 17 to 51 | |
| 9.0 |
| Fatigue Strength, MPa | 380 to 550 | |
| 250 |
| Poisson's Ratio | 0.28 | |
| 0.29 |
| Shear Modulus, GPa | 78 | |
| 86 |
| Tensile Strength: Ultimate (UTS), MPa | 700 to 1000 | |
| 700 |
| Tensile Strength: Yield (Proof), MPa | 390 to 910 | |
| 500 |
Thermal Properties
| Latent Heat of Fusion, J/g | 290 | |
| 330 |
| Melting Completion (Liquidus), °C | 1400 | |
| 1350 |
| Melting Onset (Solidus), °C | 1350 | |
| 1190 |
| Specific Heat Capacity, J/kg-K | 480 | |
| 450 |
| Thermal Conductivity, W/m-K | 14 | |
| 15 |
| Thermal Expansion, µm/m-K | 17 | |
| 11 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 2.5 | |
| 1.9 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 2.9 | |
| 2.1 |
Otherwise Unclassified Properties
| Density, g/cm3 | 7.7 | |
| 8.4 |
| Embodied Carbon, kg CO2/kg material | 3.0 | |
| 8.0 |
| Embodied Energy, MJ/kg | 43 | |
| 110 |
| Embodied Water, L/kg | 160 | |
| 520 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 160 to 310 | |
| 57 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 380 to 2070 | |
| 570 |
| Stiffness to Weight: Axial, points | 14 | |
| 15 |
| Stiffness to Weight: Bending, points | 25 | |
| 24 |
| Strength to Weight: Axial, points | 25 to 36 | |
| 23 |
| Strength to Weight: Bending, points | 23 to 29 | |
| 21 |
| Thermal Diffusivity, mm2/s | 3.8 | |
| 3.8 |
| Thermal Shock Resistance, points | 15 to 21 | |
| 21 |
Alloy Composition
| Carbon (C), % | 0 to 0.040 | |
| 0.2 to 0.35 |
| Chromium (Cr), % | 19 to 21.5 | |
| 26 to 29 |
| Cobalt (Co), % | 0 | |
| 61.7 to 67.3 |
| Iron (Fe), % | 59.5 to 67.4 | |
| 0 to 3.0 |
| Manganese (Mn), % | 8.0 to 10 | |
| 0 |
| Molybdenum (Mo), % | 0 | |
| 4.5 to 6.0 |
| Nickel (Ni), % | 5.5 to 7.5 | |
| 2.0 to 3.0 |
| Nitrogen (N), % | 0.15 to 0.4 | |
| 0 |
| Phosphorus (P), % | 0 to 0.045 | |
| 0 |
| Silicon (Si), % | 0 to 1.0 | |
| 0 to 1.5 |
| Sulfur (S), % | 0 to 0.030 | |
| 0 |