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R30021 Cobalt vs. S21800 Stainless Steel

R30021 cobalt belongs to the cobalt alloys classification, while S21800 stainless steel belongs to the iron alloys. They have a modest 22% of their average alloy composition in common, which, by itself, doesn't mean much. There are 23 material properties with values for both materials. Properties with values for just one material (14, in this case) are not shown.

For each property being compared, the top bar is R30021 cobalt and the bottom bar is S21800 stainless steel.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 220
190
Elongation at Break, % 9.0
40
Fatigue Strength, MPa 250
330
Poisson's Ratio 0.29
0.28
Shear Modulus, GPa 86
75
Tensile Strength: Ultimate (UTS), MPa 700
740
Tensile Strength: Yield (Proof), MPa 500
390

Thermal Properties

Latent Heat of Fusion, J/g 330
340
Melting Completion (Liquidus), °C 1350
1360
Melting Onset (Solidus), °C 1190
1310
Specific Heat Capacity, J/kg-K 450
500
Thermal Expansion, µm/m-K 11
16

Otherwise Unclassified Properties

Density, g/cm3 8.4
7.5
Embodied Carbon, kg CO2/kg material 8.0
3.1
Embodied Energy, MJ/kg 110
45
Embodied Water, L/kg 520
150

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 57
250
Resilience: Unit (Modulus of Resilience), kJ/m3 570
390
Stiffness to Weight: Axial, points 15
14
Stiffness to Weight: Bending, points 24
26
Strength to Weight: Axial, points 23
27
Strength to Weight: Bending, points 21
24
Thermal Shock Resistance, points 21
17

Alloy Composition

Carbon (C), % 0.2 to 0.35
0 to 0.1
Chromium (Cr), % 26 to 29
16 to 18
Cobalt (Co), % 61.7 to 67.3
0
Iron (Fe), % 0 to 3.0
59.1 to 65.4
Manganese (Mn), % 0
7.0 to 9.0
Molybdenum (Mo), % 4.5 to 6.0
0
Nickel (Ni), % 2.0 to 3.0
8.0 to 9.0
Nitrogen (N), % 0
0.080 to 0.18
Phosphorus (P), % 0
0 to 0.060
Silicon (Si), % 0 to 1.5
3.5 to 4.5
Sulfur (S), % 0
0 to 0.030