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SAE-AISI 8740 Steel vs. R31539 Cobalt

SAE-AISI 8740 steel belongs to the iron alloys classification, while R31539 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 R31539 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 190
220
Elongation at Break, % 11 to 23
13 to 22
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
1000 to 1340
Tensile Strength: Yield (Proof), MPa 380 to 570
590 to 940

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
8.2
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 190
Resilience: Unit (Modulus of Resilience), kJ/m3 390 to 850
780 to 2000
Stiffness to Weight: Axial, points 13
15
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 20 to 24
33 to 44
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
24 to 32

Alloy Composition

Aluminum (Al), % 0
0.3 to 1.0
Carbon (C), % 0.38 to 0.43
0 to 0.14
Chromium (Cr), % 0.4 to 0.6
26 to 30
Cobalt (Co), % 0
57.7 to 68.7
Iron (Fe), % 96.5 to 97.7
0 to 0.75
Lanthanum (La), % 0
0.030 to 0.2
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

Comparable Variants