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R31538 Cobalt vs. SAE-AISI 8740 Steel

R31538 cobalt belongs to the cobalt alloys classification, while SAE-AISI 8740 steel belongs to the iron 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 R31538 cobalt and the bottom bar is SAE-AISI 8740 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 220
190
Elongation at Break, % 13 to 23
11 to 23
Fatigue Strength, MPa 310 to 480
270 to 350
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 86
73
Tensile Strength: Ultimate (UTS), MPa 1020 to 1360
580 to 670
Tensile Strength: Yield (Proof), MPa 580 to 930
380 to 570

Thermal Properties

Latent Heat of Fusion, J/g 320
250
Melting Completion (Liquidus), °C 1360
1460
Melting Onset (Solidus), °C 1290
1420
Specific Heat Capacity, J/kg-K 450
470
Thermal Conductivity, W/m-K 13
39
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.0
7.3
Electrical Conductivity: Equal Weight (Specific), % IACS 2.1
8.4

Otherwise Unclassified Properties

Density, g/cm3 8.4
7.8
Embodied Carbon, kg CO2/kg material 8.1
1.5
Embodied Energy, MJ/kg 110
20
Embodied Water, L/kg 530
50

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 140 to 200
71 to 120
Resilience: Unit (Modulus of Resilience), kJ/m3 750 to 1920
390 to 850
Stiffness to Weight: Axial, points 15
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 34 to 45
20 to 24
Strength to Weight: Bending, points 27 to 32
20 to 22
Thermal Diffusivity, mm2/s 3.5
10
Thermal Shock Resistance, points 25 to 33
17 to 20

Alloy Composition

Carbon (C), % 0.15 to 0.35
0.38 to 0.43
Chromium (Cr), % 26 to 30
0.4 to 0.6
Cobalt (Co), % 58.7 to 68.9
0
Iron (Fe), % 0 to 0.75
96.5 to 97.7
Manganese (Mn), % 0 to 1.0
0.75 to 1.0
Molybdenum (Mo), % 5.0 to 7.0
0.2 to 0.3
Nickel (Ni), % 0 to 1.0
0.4 to 0.7
Nitrogen (N), % 0 to 0.25
0
Phosphorus (P), % 0
0 to 0.035
Silicon (Si), % 0 to 1.0
0.15 to 0.35
Sulfur (S), % 0
0 to 0.040

Comparable Variants