S21904 Stainless Steel vs. R31538 Cobalt
S21904 stainless steel belongs to the iron alloys classification, while R31538 cobalt belongs to the cobalt alloys. They have a modest 22% 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 R31538 cobalt.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 200 | |
| 220 |
| Elongation at Break, % | 17 to 51 | |
| 13 to 23 |
| Fatigue Strength, MPa | 380 to 550 | |
| 310 to 480 |
| Poisson's Ratio | 0.28 | |
| 0.29 |
| Shear Modulus, GPa | 78 | |
| 86 |
| Tensile Strength: Ultimate (UTS), MPa | 700 to 1000 | |
| 1020 to 1360 |
| Tensile Strength: Yield (Proof), MPa | 390 to 910 | |
| 580 to 930 |
Thermal Properties
| Latent Heat of Fusion, J/g | 290 | |
| 320 |
| Melting Completion (Liquidus), °C | 1400 | |
| 1360 |
| Melting Onset (Solidus), °C | 1350 | |
| 1290 |
| Specific Heat Capacity, J/kg-K | 480 | |
| 450 |
| Thermal Conductivity, W/m-K | 14 | |
| 13 |
| Thermal Expansion, µm/m-K | 17 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 2.5 | |
| 2.0 |
| 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 | |
| 8.1 |
| Embodied Energy, MJ/kg | 43 | |
| 110 |
| Embodied Water, L/kg | 160 | |
| 530 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 160 to 310 | |
| 140 to 200 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 380 to 2070 | |
| 750 to 1920 |
| Stiffness to Weight: Axial, points | 14 | |
| 15 |
| Stiffness to Weight: Bending, points | 25 | |
| 24 |
| Strength to Weight: Axial, points | 25 to 36 | |
| 34 to 45 |
| Strength to Weight: Bending, points | 23 to 29 | |
| 27 to 32 |
| Thermal Diffusivity, mm2/s | 3.8 | |
| 3.5 |
| Thermal Shock Resistance, points | 15 to 21 | |
| 25 to 33 |
Alloy Composition
| Carbon (C), % | 0 to 0.040 | |
| 0.15 to 0.35 |
| Chromium (Cr), % | 19 to 21.5 | |
| 26 to 30 |
| Cobalt (Co), % | 0 | |
| 58.7 to 68.9 |
| Iron (Fe), % | 59.5 to 67.4 | |
| 0 to 0.75 |
| Manganese (Mn), % | 8.0 to 10 | |
| 0 to 1.0 |
| Molybdenum (Mo), % | 0 | |
| 5.0 to 7.0 |
| Nickel (Ni), % | 5.5 to 7.5 | |
| 0 to 1.0 |
| Nitrogen (N), % | 0.15 to 0.4 | |
| 0 to 0.25 |
| Phosphorus (P), % | 0 to 0.045 | |
| 0 |
| Silicon (Si), % | 0 to 1.0 | |
| 0 to 1.0 |
| Sulfur (S), % | 0 to 0.030 | |
| 0 |