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SAE-AISI 8645 Steel vs. S21800 Stainless Steel

Both SAE-AISI 8645 steel and S21800 stainless steel are iron alloys. They have 65% of their average alloy composition in common. There are 27 material properties with values for both materials. Properties with values for just one material (8, in this case) are not shown.

For each property being compared, the top bar is SAE-AISI 8645 steel and the bottom bar is S21800 stainless steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 180 to 200
210
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 12 to 23
40
Fatigue Strength, MPa 280 to 350
330
Poisson's Ratio 0.29
0.28
Shear Modulus, GPa 73
75
Shear Strength, MPa 380 to 400
510
Tensile Strength: Ultimate (UTS), MPa 600 to 670
740
Tensile Strength: Yield (Proof), MPa 390 to 560
390

Thermal Properties

Latent Heat of Fusion, J/g 250
340
Maximum Temperature: Mechanical, °C 410
900
Melting Completion (Liquidus), °C 1460
1360
Melting Onset (Solidus), °C 1420
1310
Specific Heat Capacity, J/kg-K 470
500
Thermal Expansion, µm/m-K 13
16

Otherwise Unclassified Properties

Base Metal Price, % relative 2.6
15
Density, g/cm3 7.8
7.5
Embodied Carbon, kg CO2/kg material 1.5
3.1
Embodied Energy, MJ/kg 20
45
Embodied Water, L/kg 50
150

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 77 to 120
250
Resilience: Unit (Modulus of Resilience), kJ/m3 420 to 840
390
Stiffness to Weight: Axial, points 13
14
Stiffness to Weight: Bending, points 24
26
Strength to Weight: Axial, points 21 to 24
27
Strength to Weight: Bending, points 20 to 22
24
Thermal Shock Resistance, points 18 to 20
17

Alloy Composition

Carbon (C), % 0.43 to 0.48
0 to 0.1
Chromium (Cr), % 0.4 to 0.6
16 to 18
Iron (Fe), % 96.5 to 97.7
59.1 to 65.4
Manganese (Mn), % 0.75 to 1.0
7.0 to 9.0
Molybdenum (Mo), % 0.15 to 0.25
0
Nickel (Ni), % 0.4 to 0.7
8.0 to 9.0
Nitrogen (N), % 0
0.080 to 0.18
Phosphorus (P), % 0 to 0.035
0 to 0.060
Silicon (Si), % 0.15 to 0.35
3.5 to 4.5
Sulfur (S), % 0 to 0.040
0 to 0.030