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R30021 Cobalt vs. S31655 Stainless Steel

R30021 cobalt belongs to the cobalt alloys classification, while S31655 stainless steel belongs to the iron alloys. They have a modest 26% 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 (9, in this case) are not shown.

For each property being compared, the top bar is R30021 cobalt and the bottom bar is S31655 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
300
Poisson's Ratio 0.29
0.28
Shear Modulus, GPa 86
78
Tensile Strength: Ultimate (UTS), MPa 700
710
Tensile Strength: Yield (Proof), MPa 500
350

Thermal Properties

Latent Heat of Fusion, J/g 330
290
Melting Completion (Liquidus), °C 1350
1430
Melting Onset (Solidus), °C 1190
1380
Specific Heat Capacity, J/kg-K 450
480
Thermal Conductivity, W/m-K 15
15
Thermal Expansion, µm/m-K 11
16

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 1.9
2.4
Electrical Conductivity: Equal Weight (Specific), % IACS 2.1
2.7

Otherwise Unclassified Properties

Density, g/cm3 8.4
7.8
Embodied Carbon, kg CO2/kg material 8.0
3.3
Embodied Energy, MJ/kg 110
46
Embodied Water, L/kg 520
160

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 57
230
Resilience: Unit (Modulus of Resilience), kJ/m3 570
310
Stiffness to Weight: Axial, points 15
14
Stiffness to Weight: Bending, points 24
25
Strength to Weight: Axial, points 23
25
Strength to Weight: Bending, points 21
23
Thermal Diffusivity, mm2/s 3.8
4.0
Thermal Shock Resistance, points 21
16

Alloy Composition

Carbon (C), % 0.2 to 0.35
0 to 0.030
Chromium (Cr), % 26 to 29
19.5 to 21.5
Cobalt (Co), % 61.7 to 67.3
0
Copper (Cu), % 0
0 to 1.0
Iron (Fe), % 0 to 3.0
63.2 to 71.9
Manganese (Mn), % 0
0 to 2.0
Molybdenum (Mo), % 4.5 to 6.0
0.5 to 1.5
Nickel (Ni), % 2.0 to 3.0
8.0 to 9.5
Nitrogen (N), % 0
0.14 to 0.25
Phosphorus (P), % 0
0 to 0.045
Silicon (Si), % 0 to 1.5
0 to 1.0
Sulfur (S), % 0
0 to 0.015