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S17400 Stainless Steel vs. R30021 Cobalt

S17400 stainless steel belongs to the iron alloys classification, while R30021 cobalt belongs to the cobalt alloys. They have a modest 21% 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 (9, in this case) are not shown.

For each property being compared, the top bar is S17400 stainless steel and the bottom bar is R30021 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 190
220
Elongation at Break, % 11 to 21
9.0
Fatigue Strength, MPa 380 to 670
250
Poisson's Ratio 0.28
0.29
Rockwell C Hardness 27 to 43
32
Shear Modulus, GPa 75
86
Tensile Strength: Ultimate (UTS), MPa 910 to 1390
700
Tensile Strength: Yield (Proof), MPa 580 to 1250
500

Thermal Properties

Latent Heat of Fusion, J/g 280
330
Melting Completion (Liquidus), °C 1440
1350
Melting Onset (Solidus), °C 1400
1190
Specific Heat Capacity, J/kg-K 480
450
Thermal Conductivity, W/m-K 17
15
Thermal Expansion, µm/m-K 11
11

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.3
1.9
Electrical Conductivity: Equal Weight (Specific), % IACS 2.6
2.1

Otherwise Unclassified Properties

Density, g/cm3 7.8
8.4
Embodied Carbon, kg CO2/kg material 2.7
8.0
Embodied Energy, MJ/kg 39
110
Embodied Water, L/kg 130
520

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 140 to 160
57
Resilience: Unit (Modulus of Resilience), kJ/m3 880 to 4060
570
Stiffness to Weight: Axial, points 14
15
Stiffness to Weight: Bending, points 25
24
Strength to Weight: Axial, points 32 to 49
23
Strength to Weight: Bending, points 27 to 35
21
Thermal Diffusivity, mm2/s 4.5
3.8
Thermal Shock Resistance, points 30 to 46
21

Alloy Composition

Carbon (C), % 0 to 0.070
0.2 to 0.35
Chromium (Cr), % 15 to 17
26 to 29
Cobalt (Co), % 0
61.7 to 67.3
Copper (Cu), % 3.0 to 5.0
0
Iron (Fe), % 70.4 to 78.9
0 to 3.0
Manganese (Mn), % 0 to 1.0
0
Molybdenum (Mo), % 0
4.5 to 6.0
Nickel (Ni), % 3.0 to 5.0
2.0 to 3.0
Niobium (Nb), % 0.15 to 0.45
0
Phosphorus (P), % 0 to 0.040
0
Silicon (Si), % 0 to 1.0
0 to 1.5
Sulfur (S), % 0 to 0.030
0