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R30012 Cobalt vs. S81921 Stainless Steel

R30012 cobalt belongs to the cobalt alloys classification, while S81921 stainless steel belongs to the iron alloys. They have a modest 25% 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 (7, in this case) are not shown.

For each property being compared, the top bar is R30012 cobalt and the bottom bar is S81921 stainless steel.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 220
200
Elongation at Break, % 1.0
29
Fatigue Strength, MPa 320
370
Poisson's Ratio 0.28
0.28
Rockwell C Hardness 48
27
Shear Modulus, GPa 86
79
Tensile Strength: Ultimate (UTS), MPa 830
710
Tensile Strength: Yield (Proof), MPa 650
500

Thermal Properties

Latent Heat of Fusion, J/g 320
290
Melting Completion (Liquidus), °C 1470
1430
Melting Onset (Solidus), °C 1280
1390
Specific Heat Capacity, J/kg-K 440
480
Thermal Conductivity, W/m-K 15
15
Thermal Expansion, µm/m-K 12
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 1.8
2.2
Electrical Conductivity: Equal Weight (Specific), % IACS 1.8
2.5

Otherwise Unclassified Properties

Density, g/cm3 8.8
7.7
Embodied Carbon, kg CO2/kg material 8.3
2.9
Embodied Energy, MJ/kg 120
41
Embodied Water, L/kg 480
150

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 7.7
180
Resilience: Unit (Modulus of Resilience), kJ/m3 960
630
Stiffness to Weight: Axial, points 14
14
Stiffness to Weight: Bending, points 23
25
Strength to Weight: Axial, points 26
25
Strength to Weight: Bending, points 22
23
Thermal Diffusivity, mm2/s 3.8
4.0
Thermal Shock Resistance, points 23
20

Alloy Composition

Carbon (C), % 1.4 to 2.0
0 to 0.030
Chromium (Cr), % 27 to 32
19 to 22
Cobalt (Co), % 47.5 to 64.1
0
Iron (Fe), % 0 to 3.0
66.7 to 75.9
Manganese (Mn), % 0
2.0 to 4.0
Molybdenum (Mo), % 0 to 1.0
1.0 to 2.0
Nickel (Ni), % 0 to 3.0
2.0 to 4.0
Nitrogen (N), % 0
0.14 to 0.2
Phosphorus (P), % 0
0 to 0.040
Silicon (Si), % 0 to 2.0
0 to 1.0
Sulfur (S), % 0
0 to 0.030
Tungsten (W), % 7.5 to 9.5
0