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SAE-AISI 8740 Steel vs. R30012 Cobalt

SAE-AISI 8740 steel belongs to the iron alloys classification, while R30012 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 R30012 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 190
220
Elongation at Break, % 11 to 23
1.0
Fatigue Strength, MPa 270 to 350
320
Poisson's Ratio 0.29
0.28
Shear Modulus, GPa 73
86
Tensile Strength: Ultimate (UTS), MPa 580 to 670
830
Tensile Strength: Yield (Proof), MPa 380 to 570
650

Thermal Properties

Latent Heat of Fusion, J/g 250
320
Melting Completion (Liquidus), °C 1460
1470
Melting Onset (Solidus), °C 1420
1280
Specific Heat Capacity, J/kg-K 470
440
Thermal Conductivity, W/m-K 39
15
Thermal Expansion, µm/m-K 13
12

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.3
1.8
Electrical Conductivity: Equal Weight (Specific), % IACS 8.4
1.8

Otherwise Unclassified Properties

Density, g/cm3 7.8
8.8
Embodied Carbon, kg CO2/kg material 1.5
8.3
Embodied Energy, MJ/kg 20
120
Embodied Water, L/kg 50
480

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 71 to 120
7.7
Resilience: Unit (Modulus of Resilience), kJ/m3 390 to 850
960
Stiffness to Weight: Axial, points 13
14
Stiffness to Weight: Bending, points 24
23
Strength to Weight: Axial, points 20 to 24
26
Strength to Weight: Bending, points 20 to 22
22
Thermal Diffusivity, mm2/s 10
3.8
Thermal Shock Resistance, points 17 to 20
23

Alloy Composition

Carbon (C), % 0.38 to 0.43
1.4 to 2.0
Chromium (Cr), % 0.4 to 0.6
27 to 32
Cobalt (Co), % 0
47.5 to 64.1
Iron (Fe), % 96.5 to 97.7
0 to 3.0
Manganese (Mn), % 0.75 to 1.0
0
Molybdenum (Mo), % 0.2 to 0.3
0 to 1.0
Nickel (Ni), % 0.4 to 0.7
0 to 3.0
Phosphorus (P), % 0 to 0.035
0
Silicon (Si), % 0.15 to 0.35
0 to 2.0
Sulfur (S), % 0 to 0.040
0
Tungsten (W), % 0
7.5 to 9.5