ASTM A387 Grade 91 Class 2 vs. G-CoCr28 Cobalt
ASTM A387 grade 91 class 2 belongs to the iron alloys classification, while G-CoCr28 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 27 material properties with values for both materials. Properties with values for just one material (5, in this case) are not shown.
For each property being compared, the top bar is ASTM A387 grade 91 class 2 and the bottom bar is G-CoCr28 cobalt.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 190 | |
| 210 |
| Elongation at Break, % | 20 | |
| 6.7 |
| Fatigue Strength, MPa | 330 | |
| 130 |
| Poisson's Ratio | 0.28 | |
| 0.28 |
| Shear Modulus, GPa | 75 | |
| 83 |
| Tensile Strength: Ultimate (UTS), MPa | 670 | |
| 560 |
| Tensile Strength: Yield (Proof), MPa | 470 | |
| 260 |
Thermal Properties
| Latent Heat of Fusion, J/g | 270 | |
| 320 |
| Maximum Temperature: Mechanical, °C | 600 | |
| 1200 |
| Melting Completion (Liquidus), °C | 1460 | |
| 1330 |
| Melting Onset (Solidus), °C | 1420 | |
| 1270 |
| Specific Heat Capacity, J/kg-K | 470 | |
| 470 |
| Thermal Conductivity, W/m-K | 26 | |
| 8.5 |
| Thermal Expansion, µm/m-K | 13 | |
| 14 |
Otherwise Unclassified Properties
| Base Metal Price, % relative | 7.0 | |
| 100 |
| Density, g/cm3 | 7.8 | |
| 8.1 |
| Embodied Carbon, kg CO2/kg material | 2.6 | |
| 6.2 |
| Embodied Energy, MJ/kg | 37 | |
| 84 |
| Embodied Water, L/kg | 88 | |
| 440 |
Common Calculations
| Resilience: Ultimate (Unit Rupture Work), MJ/m3 | 120 | |
| 31 |
| Resilience: Unit (Modulus of Resilience), kJ/m3 | 580 | |
| 160 |
| Stiffness to Weight: Axial, points | 14 | |
| 15 |
| Stiffness to Weight: Bending, points | 25 | |
| 24 |
| Strength to Weight: Axial, points | 24 | |
| 19 |
| Strength to Weight: Bending, points | 22 | |
| 19 |
| Thermal Diffusivity, mm2/s | 6.9 | |
| 2.2 |
| Thermal Shock Resistance, points | 19 | |
| 14 |
Alloy Composition
| Aluminum (Al), % | 0 to 0.020 | |
| 0 |
| Carbon (C), % | 0.080 to 0.12 | |
| 0.050 to 0.25 |
| Chromium (Cr), % | 8.0 to 9.5 | |
| 27 to 30 |
| Cobalt (Co), % | 0 | |
| 48 to 52 |
| Iron (Fe), % | 87.3 to 90.3 | |
| 9.7 to 24.5 |
| Manganese (Mn), % | 0.3 to 0.6 | |
| 0 to 1.5 |
| Molybdenum (Mo), % | 0.85 to 1.1 | |
| 0 to 0.5 |
| Nickel (Ni), % | 0 to 0.4 | |
| 0 to 4.0 |
| Niobium (Nb), % | 0.060 to 0.1 | |
| 0 to 0.5 |
| Nitrogen (N), % | 0.030 to 0.070 | |
| 0 |
| Phosphorus (P), % | 0 to 0.020 | |
| 0 to 0.040 |
| Silicon (Si), % | 0.2 to 0.5 | |
| 0.5 to 1.5 |
| Sulfur (S), % | 0 to 0.010 | |
| 0 to 0.030 |
| Titanium (Ti), % | 0 to 0.010 | |
| 0 |
| Vanadium (V), % | 0.18 to 0.25 | |
| 0 |
| Zirconium (Zr), % | 0 to 0.010 | |
| 0 |