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S21640 Stainless Steel vs. R30021 Cobalt

S21640 stainless steel belongs to the iron alloys classification, while R30021 cobalt belongs to the cobalt alloys. They have a modest 24% 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 (8, in this case) are not shown.

For each property being compared, the top bar is S21640 stainless steel and the bottom bar is R30021 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 200
220
Elongation at Break, % 46
9.0
Fatigue Strength, MPa 320
250
Poisson's Ratio 0.28
0.29
Shear Modulus, GPa 78
86
Tensile Strength: Ultimate (UTS), MPa 740
700
Tensile Strength: Yield (Proof), MPa 350
500

Thermal Properties

Latent Heat of Fusion, J/g 290
330
Melting Completion (Liquidus), °C 1430
1350
Melting Onset (Solidus), °C 1380
1190
Specific Heat Capacity, J/kg-K 480
450
Thermal Conductivity, W/m-K 15
15
Thermal Expansion, µm/m-K 17
11

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.4
1.9
Electrical Conductivity: Equal Weight (Specific), % IACS 2.8
2.1

Otherwise Unclassified Properties

Density, g/cm3 7.7
8.4
Embodied Carbon, kg CO2/kg material 3.6
8.0
Embodied Energy, MJ/kg 51
110
Embodied Water, L/kg 150
520

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 280
57
Resilience: Unit (Modulus of Resilience), kJ/m3 300
570
Stiffness to Weight: Axial, points 14
15
Stiffness to Weight: Bending, points 25
24
Strength to Weight: Axial, points 27
23
Strength to Weight: Bending, points 23
21
Thermal Diffusivity, mm2/s 4.0
3.8
Thermal Shock Resistance, points 16
21

Alloy Composition

Carbon (C), % 0 to 0.080
0.2 to 0.35
Chromium (Cr), % 17.5 to 19.5
26 to 29
Cobalt (Co), % 0
61.7 to 67.3
Iron (Fe), % 63 to 74.3
0 to 3.0
Manganese (Mn), % 3.5 to 6.5
0
Molybdenum (Mo), % 0.5 to 2.0
4.5 to 6.0
Nickel (Ni), % 4.0 to 6.5
2.0 to 3.0
Niobium (Nb), % 0.1 to 1.0
0
Nitrogen (N), % 0.080 to 0.3
0
Phosphorus (P), % 0 to 0.060
0
Silicon (Si), % 0 to 1.0
0 to 1.5
Sulfur (S), % 0 to 0.030
0