AISI 418 (Alloy 615, S41800) Stainless Steel
AISI 418 stainless steel is a martensitic stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the heat treated (HT) condition. 418 is the AISI designation for this material. S41800 is the UNS number. And Alloy 615 is the common industry name.
It has a fairly high base cost among wrought martensitic stainless steels. In addition, it has a fairly high tensile strength and a moderately high embodied energy.
The graph bars on the material properties cards below compare AISI 418 stainless steel to: wrought martensitic stainless steels (top), all iron alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.
Mechanical Properties
Brinell Hardness
330
Elastic (Young's, Tensile) Modulus
200 GPa 29 x 106 psi
Elongation at Break
17 %
Fatigue Strength
520 MPa 75 x 103 psi
Poisson's Ratio
0.28
Reduction in Area
50 %
Shear Modulus
77 GPa 11 x 106 psi
Shear Strength
680 MPa 98 x 103 psi
Tensile Strength: Ultimate (UTS)
1100 MPa 160 x 103 psi
Tensile Strength: Yield (Proof)
850 MPa 120 x 103 psi
Thermal Properties
Latent Heat of Fusion
270 J/g
Maximum Temperature: Corrosion
390 °C 730 °F
Maximum Temperature: Mechanical
770 °C 1410 °F
Melting Completion (Liquidus)
1500 °C 2740 °F
Melting Onset (Solidus)
1460 °C 2660 °F
Specific Heat Capacity
470 J/kg-K 0.11 BTU/lb-°F
Thermal Conductivity
25 W/m-K 15 BTU/h-ft-°F
Thermal Expansion
10 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
2.8 % IACS
Electrical Conductivity: Equal Weight (Specific)
3.1 % IACS
Otherwise Unclassified Properties
Base Metal Price
15 % relative
Density
8.0 g/cm3 500 lb/ft3
Embodied Carbon
2.9 kg CO2/kg material
Embodied Energy
41 MJ/kg 18 x 103 BTU/lb
Embodied Water
110 L/kg 13 gal/lb
Common Calculations
PREN (Pitting Resistance)
19
Resilience: Ultimate (Unit Rupture Work)
170 MJ/m3
Resilience: Unit (Modulus of Resilience)
1830 kJ/m3
Stiffness to Weight: Axial
14 points
Stiffness to Weight: Bending
24 points
Strength to Weight: Axial
38 points
Strength to Weight: Bending
29 points
Thermal Diffusivity
6.7 mm2/s
Thermal Shock Resistance
40 points
Alloy Composition
Among wrought stainless steels, the composition of AISI 418 stainless steel is notable for including tungsten (W). Tungsten interacts with other alloying elements to a greater extent than usual, which makes it hard to broadly characterize its effects.
| Fe | 78.5 to 83.6 | |
| Cr | 12 to 14 | |
| W | 2.5 to 3.5 | |
| Ni | 1.8 to 2.2 | |
| Mn | 0 to 0.5 | |
| Si | 0 to 0.5 | |
| Mo | 0 to 0.5 | |
| C | 0.15 to 0.2 | |
| P | 0 to 0.040 | |
| S | 0 to 0.030 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
ASTM A565: Standard Specification for Martensitic Stainless Steel Bars for High-Temperature Service
Advanced Materials in Automotive Engineering, Jason Rowe (editor), 2012
ASTM A959: Standard Guide for Specifying Harmonized Standard Grade Compositions for Wrought Stainless Steels
Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993
Corrosion of Stainless Steels, A. John Sedriks, 1996
ASM Specialty Handbook: Stainless Steels, J. R. Davis (editor), 1994
Advances in Stainless Steels, Baldev Raj et al. (editors), 2010
CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015