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R30021 Cobalt vs. S35125 Stainless Steel

R30021 cobalt belongs to the cobalt alloys classification, while S35125 stainless steel belongs to the iron alloys. They have a modest 28% 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 (7, in this case) are not shown.

For each property being compared, the top bar is R30021 cobalt and the bottom bar is S35125 stainless steel.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 220
200
Elongation at Break, % 9.0
39
Fatigue Strength, MPa 250
200
Poisson's Ratio 0.29
0.28
Shear Modulus, GPa 86
78
Tensile Strength: Ultimate (UTS), MPa 700
540
Tensile Strength: Yield (Proof), MPa 500
230

Thermal Properties

Latent Heat of Fusion, J/g 330
300
Melting Completion (Liquidus), °C 1350
1430
Melting Onset (Solidus), °C 1190
1380
Specific Heat Capacity, J/kg-K 450
470
Thermal Conductivity, W/m-K 15
12
Thermal Expansion, µm/m-K 11
16

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 1.9
1.7
Electrical Conductivity: Equal Weight (Specific), % IACS 2.1
1.9

Otherwise Unclassified Properties

Density, g/cm3 8.4
8.1
Embodied Carbon, kg CO2/kg material 8.0
6.4
Embodied Energy, MJ/kg 110
89
Embodied Water, L/kg 520
210

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 57
170
Resilience: Unit (Modulus of Resilience), kJ/m3 570
140
Stiffness to Weight: Axial, points 15
14
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 23
19
Strength to Weight: Bending, points 21
18
Thermal Diffusivity, mm2/s 3.8
3.1
Thermal Shock Resistance, points 21
12

Alloy Composition

Carbon (C), % 0.2 to 0.35
0 to 0.1
Chromium (Cr), % 26 to 29
20 to 23
Cobalt (Co), % 61.7 to 67.3
0
Iron (Fe), % 0 to 3.0
36.2 to 45.8
Manganese (Mn), % 0
1.0 to 1.5
Molybdenum (Mo), % 4.5 to 6.0
2.0 to 3.0
Nickel (Ni), % 2.0 to 3.0
31 to 35
Niobium (Nb), % 0
0.25 to 0.6
Phosphorus (P), % 0
0 to 0.045
Silicon (Si), % 0 to 1.5
0 to 0.5
Sulfur (S), % 0
0 to 0.015