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SAE-AISI A8 Steel vs. R30021 Cobalt

SAE-AISI A8 steel belongs to the iron alloys classification, while R30021 cobalt belongs to the cobalt alloys. There are 22 material properties with values for both materials. Properties with values for just one material (9, in this case) are not shown.

For each property being compared, the top bar is SAE-AISI A8 steel and the bottom bar is R30021 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 190
220
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 74
86
Tensile Strength: Ultimate (UTS), MPa 700 to 1920
700

Thermal Properties

Latent Heat of Fusion, J/g 270
330
Melting Completion (Liquidus), °C 1480
1350
Melting Onset (Solidus), °C 1430
1190
Specific Heat Capacity, J/kg-K 470
450
Thermal Conductivity, W/m-K 37
15
Thermal Expansion, µm/m-K 12
11

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 8.3
1.9
Electrical Conductivity: Equal Weight (Specific), % IACS 9.5
2.1

Otherwise Unclassified Properties

Density, g/cm3 7.9
8.4
Embodied Carbon, kg CO2/kg material 2.3
8.0
Embodied Energy, MJ/kg 31
110
Embodied Water, L/kg 73
520

Common Calculations

Stiffness to Weight: Axial, points 14
15
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 25 to 68
23
Strength to Weight: Bending, points 22 to 44
21
Thermal Diffusivity, mm2/s 9.9
3.8
Thermal Shock Resistance, points 22 to 62
21

Alloy Composition

Carbon (C), % 0.5 to 0.6
0.2 to 0.35
Chromium (Cr), % 4.8 to 5.5
26 to 29
Cobalt (Co), % 0
61.7 to 67.3
Copper (Cu), % 0 to 0.25
0
Iron (Fe), % 88.5 to 91.9
0 to 3.0
Manganese (Mn), % 0 to 0.5
0
Molybdenum (Mo), % 1.2 to 1.7
4.5 to 6.0
Nickel (Ni), % 0 to 0.3
2.0 to 3.0
Phosphorus (P), % 0 to 0.030
0
Silicon (Si), % 0.75 to 1.1
0 to 1.5
Sulfur (S), % 0 to 0.030
0
Tungsten (W), % 1.0 to 1.5
0