SAE-AISI 8740 Steel vs. R31538 Cobalt
SAE-AISI 8740 steel belongs to the iron alloys classification, while R31538 cobalt belongs to the cobalt alloys. There are 27 material properties with values for both materials. Properties with values for just one material (6, in this case) are not shown.
For each property being compared, the top bar is SAE-AISI 8740 steel and the bottom bar is R31538 cobalt.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 220 |
| Elongation at Break, % | 11 to 23 | |
| 13 to 23 |
| Fatigue Strength, MPa | 270 to 350 | |
| 310 to 480 |
| Poisson's Ratio | 0.29 | |
| 0.29 |
| Shear Modulus, GPa | 73 | |
| 86 |
| Tensile Strength: Ultimate (UTS), MPa | 580 to 670 | |
| 1020 to 1360 |
| Tensile Strength: Yield (Proof), MPa | 380 to 570 | |
| 580 to 930 |
Thermal Properties
| Latent Heat of Fusion, J/g | 250 | |
| 320 |
| Melting Completion (Liquidus), °C | 1460 | |
| 1360 |
| Melting Onset (Solidus), °C | 1420 | |
| 1290 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 450 |
| Thermal Conductivity, W/m-K | 39 | |
| 13 |
| Thermal Expansion, µm/m-K | 13 | |
| 13 |
Electrical Properties
| Electrical Conductivity: Equal Volume, % IACS | 7.3 | |
| 2.0 |
| Electrical Conductivity: Equal Weight (Specific), % IACS | 8.4 | |
| 2.1 |
Otherwise Unclassified Properties
| Density, g/cm3 | 7.8 | |
| 8.4 |
| Embodied Carbon, kg CO2/kg material | 1.5 | |
| 8.1 |
| Embodied Energy, MJ/kg | 20 | |
| 110 |
| Embodied Water, L/kg | 50 | |
| 530 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 71 to 120 | |
| 140 to 200 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 390 to 850 | |
| 750 to 1920 |
| Stiffness to Weight: Axial, points | 13 | |
| 15 |
| Stiffness to Weight: Bending, points | 24 | |
| 24 |
| Strength to Weight: Axial, points | 20 to 24 | |
| 34 to 45 |
| Strength to Weight: Bending, points | 20 to 22 | |
| 27 to 32 |
| Thermal Diffusivity, mm2/s | 10 | |
| 3.5 |
| Thermal Shock Resistance, points | 17 to 20 | |
| 25 to 33 |
Alloy Composition
| Carbon (C), % | 0.38 to 0.43 | |
| 0.15 to 0.35 |
| Chromium (Cr), % | 0.4 to 0.6 | |
| 26 to 30 |
| Cobalt (Co), % | 0 | |
| 58.7 to 68.9 |
| Iron (Fe), % | 96.5 to 97.7 | |
| 0 to 0.75 |
| Manganese (Mn), % | 0.75 to 1.0 | |
| 0 to 1.0 |
| Molybdenum (Mo), % | 0.2 to 0.3 | |
| 5.0 to 7.0 |
| Nickel (Ni), % | 0.4 to 0.7 | |
| 0 to 1.0 |
| Nitrogen (N), % | 0 | |
| 0 to 0.25 |
| Phosphorus (P), % | 0 to 0.035 | |
| 0 |
| Silicon (Si), % | 0.15 to 0.35 | |
| 0 to 1.0 |
| Sulfur (S), % | 0 to 0.040 | |
| 0 |