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S21900 Stainless Steel vs. R30816 Cobalt

S21900 stainless steel belongs to the iron alloys classification, while R30816 cobalt belongs to the cobalt alloys. They have a modest 31% 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 S21900 stainless steel and the bottom bar is R30816 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 220
280
Elastic (Young's, Tensile) Modulus, GPa 200
210
Elongation at Break, % 50
23
Fatigue Strength, MPa 380
250
Poisson's Ratio 0.28
0.3
Reduction in Area, % 57
22
Shear Modulus, GPa 78
81
Tensile Strength: Ultimate (UTS), MPa 710
1020
Tensile Strength: Yield (Proof), MPa 390
460

Thermal Properties

Latent Heat of Fusion, J/g 290
300
Melting Completion (Liquidus), °C 1400
1540
Melting Onset (Solidus), °C 1350
1460
Specific Heat Capacity, J/kg-K 480
420
Thermal Conductivity, W/m-K 14
13
Thermal Expansion, µm/m-K 17
12

Otherwise Unclassified Properties

Density, g/cm3 7.7
9.1
Embodied Carbon, kg CO2/kg material 3.0
20
Embodied Energy, MJ/kg 43
320
Embodied Water, L/kg 160
440

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 300
190
Resilience: Unit (Modulus of Resilience), kJ/m3 380
510
Stiffness to Weight: Axial, points 14
13
Stiffness to Weight: Bending, points 25
22
Strength to Weight: Axial, points 26
31
Strength to Weight: Bending, points 23
25
Thermal Diffusivity, mm2/s 3.8
3.3
Thermal Shock Resistance, points 15
28

Alloy Composition

Carbon (C), % 0 to 0.080
0.32 to 0.42
Chromium (Cr), % 19 to 21.5
19 to 21
Cobalt (Co), % 0
40 to 49.8
Iron (Fe), % 59.4 to 67.4
0 to 5.0
Manganese (Mn), % 8.0 to 10
1.0 to 2.0
Molybdenum (Mo), % 0
3.5 to 4.5
Nickel (Ni), % 5.5 to 7.5
19 to 21
Niobium (Nb), % 0
3.5 to 4.5
Nitrogen (N), % 0.15 to 0.4
0
Phosphorus (P), % 0 to 0.045
0 to 0.040
Silicon (Si), % 0 to 1.0
0 to 1.0
Sulfur (S), % 0 to 0.030
0 to 0.030
Tantalum (Ta), % 0
3.5 to 4.5
Tungsten (W), % 0
3.5 to 4.5