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S21900 Stainless Steel vs. R30075 Cobalt

S21900 stainless steel belongs to the iron alloys classification, while R30075 cobalt belongs to the cobalt alloys. They have a modest 22% of their average alloy composition in common, which, by itself, doesn't mean much. There are 28 material properties with values for both materials. Properties with values for just one material (6, in this case) are not shown.

For each property being compared, the top bar is S21900 stainless steel and the bottom bar is R30075 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 200
210 to 250
Elongation at Break, % 50
12
Fatigue Strength, MPa 380
250 to 840
Poisson's Ratio 0.28
0.29
Reduction in Area, % 57
20
Shear Modulus, GPa 78
82 to 98
Tensile Strength: Ultimate (UTS), MPa 710
780 to 1280
Tensile Strength: Yield (Proof), MPa 390
480 to 840

Thermal Properties

Latent Heat of Fusion, J/g 290
320
Melting Completion (Liquidus), °C 1400
1360
Melting Onset (Solidus), °C 1350
1290
Specific Heat Capacity, J/kg-K 480
450
Thermal Conductivity, W/m-K 14
13
Thermal Expansion, µm/m-K 17
12

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.5
2.0
Electrical Conductivity: Equal Weight (Specific), % IACS 2.9
2.1

Otherwise Unclassified Properties

Density, g/cm3 7.7
8.4
Embodied Carbon, kg CO2/kg material 3.0
8.1
Embodied Energy, MJ/kg 43
110
Embodied Water, L/kg 160
530

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 300
84 to 140
Resilience: Unit (Modulus of Resilience), kJ/m3 380
560 to 1410
Stiffness to Weight: Axial, points 14
14 to 17
Stiffness to Weight: Bending, points 25
24 to 25
Strength to Weight: Axial, points 26
26 to 42
Strength to Weight: Bending, points 23
22 to 31
Thermal Diffusivity, mm2/s 3.8
3.5
Thermal Shock Resistance, points 15
21 to 29

Alloy Composition

Aluminum (Al), % 0
0 to 0.1
Boron (B), % 0
0 to 0.010
Carbon (C), % 0 to 0.080
0 to 0.35
Chromium (Cr), % 19 to 21.5
27 to 30
Cobalt (Co), % 0
58.7 to 68
Iron (Fe), % 59.4 to 67.4
0 to 0.75
Manganese (Mn), % 8.0 to 10
0 to 1.0
Molybdenum (Mo), % 0
5.0 to 7.0
Nickel (Ni), % 5.5 to 7.5
0 to 0.5
Nitrogen (N), % 0.15 to 0.4
0 to 0.25
Phosphorus (P), % 0 to 0.045
0 to 0.020
Silicon (Si), % 0 to 1.0
0 to 1.0
Sulfur (S), % 0 to 0.030
0 to 0.010
Titanium (Ti), % 0
0 to 0.1
Tungsten (W), % 0
0 to 0.2