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ACI-ASTM CF8 Steel vs. R31233 Cobalt

ACI-ASTM CF8 steel belongs to the iron alloys classification, while R31233 cobalt belongs to the cobalt alloys. They have a modest 33% 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 ACI-ASTM CF8 steel and the bottom bar is R31233 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 200
220
Elongation at Break, % 55
17
Fatigue Strength, MPa 260
220
Poisson's Ratio 0.28
0.29
Shear Modulus, GPa 77
85
Tensile Strength: Ultimate (UTS), MPa 540
1020
Tensile Strength: Yield (Proof), MPa 260
420

Thermal Properties

Latent Heat of Fusion, J/g 300
320
Melting Completion (Liquidus), °C 1420
1350
Melting Onset (Solidus), °C 1430
1330
Specific Heat Capacity, J/kg-K 480
440
Thermal Conductivity, W/m-K 16
12
Thermal Expansion, µm/m-K 15
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.0
2.0
Electrical Conductivity: Equal Weight (Specific), % IACS 2.3
2.1

Otherwise Unclassified Properties

Density, g/cm3 7.8
8.6
Embodied Carbon, kg CO2/kg material 3.1
8.4
Embodied Energy, MJ/kg 44
110
Embodied Water, L/kg 150
480

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 240
140
Resilience: Unit (Modulus of Resilience), kJ/m3 160
410
Stiffness to Weight: Axial, points 14
14
Stiffness to Weight: Bending, points 25
23
Strength to Weight: Axial, points 19
33
Strength to Weight: Bending, points 19
26
Thermal Diffusivity, mm2/s 4.3
3.2
Thermal Shock Resistance, points 13
25

Alloy Composition

Boron (B), % 0
0 to 0.015
Carbon (C), % 0 to 0.080
0.020 to 0.1
Chromium (Cr), % 18 to 21
23.5 to 27.5
Cobalt (Co), % 0
44.7 to 63.3
Iron (Fe), % 63.8 to 74
1.0 to 5.0
Manganese (Mn), % 0 to 1.5
0.1 to 1.5
Molybdenum (Mo), % 0 to 0.5
4.0 to 6.0
Nickel (Ni), % 8.0 to 11
7.0 to 11
Nitrogen (N), % 0
0.030 to 0.12
Phosphorus (P), % 0 to 0.040
0 to 0.030
Silicon (Si), % 0 to 2.0
0.050 to 1.0
Sulfur (S), % 0 to 0.040
0 to 0.020
Tungsten (W), % 0
1.0 to 3.0