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R31538 Cobalt vs. ASTM A387 Grade 21 Steel

R31538 cobalt belongs to the cobalt alloys classification, while ASTM A387 grade 21 steel belongs to the iron alloys. 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 R31538 cobalt and the bottom bar is ASTM A387 grade 21 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 220
190
Elongation at Break, % 13 to 23
21
Fatigue Strength, MPa 310 to 480
160 to 250
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 86
74
Tensile Strength: Ultimate (UTS), MPa 1020 to 1360
500 to 590
Tensile Strength: Yield (Proof), MPa 580 to 930
230 to 350

Thermal Properties

Latent Heat of Fusion, J/g 320
260
Melting Completion (Liquidus), °C 1360
1470
Melting Onset (Solidus), °C 1290
1430
Specific Heat Capacity, J/kg-K 450
470
Thermal Conductivity, W/m-K 13
41
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.0
7.6
Electrical Conductivity: Equal Weight (Specific), % IACS 2.1
8.8

Otherwise Unclassified Properties

Density, g/cm3 8.4
7.9
Embodied Carbon, kg CO2/kg material 8.1
1.8
Embodied Energy, MJ/kg 110
23
Embodied Water, L/kg 530
62

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 140 to 200
84 to 110
Resilience: Unit (Modulus of Resilience), kJ/m3 750 to 1920
140 to 320
Stiffness to Weight: Axial, points 15
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 34 to 45
18 to 21
Strength to Weight: Bending, points 27 to 32
18 to 20
Thermal Diffusivity, mm2/s 3.5
11
Thermal Shock Resistance, points 25 to 33
14 to 17

Alloy Composition

Carbon (C), % 0.15 to 0.35
0.050 to 0.15
Chromium (Cr), % 26 to 30
2.8 to 3.3
Cobalt (Co), % 58.7 to 68.9
0
Iron (Fe), % 0 to 0.75
94.4 to 96
Manganese (Mn), % 0 to 1.0
0.3 to 0.6
Molybdenum (Mo), % 5.0 to 7.0
0.9 to 1.1
Nickel (Ni), % 0 to 1.0
0
Nitrogen (N), % 0 to 0.25
0
Phosphorus (P), % 0
0 to 0.025
Silicon (Si), % 0 to 1.0
0 to 0.5
Sulfur (S), % 0
0 to 0.025

Comparable Variants