Martensitic stainless grades such as 1.4021 and 1.4418

Martensitic stainless steels combine chromium-based corrosion resistance with the ability to develop relatively high strength and hardness through heat treatment.

Two EN grades that can appear in mechanical, pump, valve and energy-sector enquiries are 1.4021 and 1.4418.

They are both martensitic stainless steels, but they are not close substitutes.

1.4021 — X20Cr13

1.4021 is a conventional chromium martensitic stainless grade.

Outokumpu maps it to the Type 420 family and lists:

• EN material number 1.4021;
• EN name X20Cr13;
• ASTM/UNS family Type 420 / S42000.

The grade contains roughly 13% chromium and significantly more carbon than low-carbon soft-martensitic grades.

Typical applications include:

• mechanical parts;
• flanges and valves;
• cutting/surgical components;
• wear-resistant parts;
• brake-disc and press-plate applications.

Its final strength, hardness, toughness and corrosion behaviour depend strongly on heat treatment.

1.4418 — X4CrNiMo16-5-1

1.4418 is a different type of martensitic stainless steel, often described as soft martensitic or low-carbon Cr-Ni-Mo martensitic stainless.

Böhler lists:

• material number 1.4418;
• EN name X4CrNiMo16-5-1;
• carbon maximum around 0.06%;
• chromium around 15–17%;
• nickel around 4–6%;
• molybdenum around 0.8–1.5%.

Compared with a conventional 13% Cr martensitic grade, the added Ni and Mo and lower carbon support a useful combination of strength, toughness, weldability and corrosion resistance.

Applications include:

• pump and high-pressure components;
• shafts;
• turbine/compressor components;
• valves and actuators;
• oil-and-gas mechanical components.

1.4418 does not have a simple AISI equivalent

This is an important procurement point.

A historical conversation tried to identify U.S. alternatives such as 431 or 17-4 PH. Those materials can be comparable in selected properties or applications, but they are not direct equivalents to 1.4418.

Unlike 1.4021, which sits clearly in the Type 420/UNS S42000 family, 1.4418 should not be converted to one simple AISI label.

If a U.S.-specification substitute is required, compare chemistry, strength condition, impact toughness, corrosion performance, weldability and the governing product standard.

See How to compare steel grades across standards.

Heat-treatment condition matters

Martensitic stainless steels are commonly supplied in specific hardened-and-tempered or annealed conditions depending on grade, product form and required properties.

For 1.4418, the same chemistry can be supplied to different quenched-and-tempered strength classes. Therefore the material number alone is not enough to define the mechanical properties.

This is a different heat-treatment concept from the solution annealing used for austenitic and duplex stainless steels.

Corrosion resistance should not be generalized from the word “stainless”

Martensitic stainless steels generally do not have the same corrosion profile as high-alloy austenitic or duplex grades.

Surface finish, heat treatment, tempering condition and service medium all matter.

For aggressive chloride environments, a grade such as 1.4418 should not be assumed equivalent to 316L or duplex simply because its chromium content is higher than a basic martensitic grade.

MetalMate takeaway

1.4021 and 1.4418 are both martensitic stainless steels but belong to different chemistry/strength concepts. 1.4021 maps to the Type 420 family; 1.4418 is a low-carbon Cr-Ni-Mo soft-martensitic grade with no simple AISI one-to-one equivalent. Always specify the heat-treatment/strength condition as well as the grade.

Related Knowledge

• How to compare steel grades across standards
• Solution annealing of stainless and duplex steel

References

• Outokumpu, Dura 420/4021 — EN 1.4021, Type 420 / UNS S42000: https://www.outokumpu.com/products/product-ranges/dura
• BÖHLER, N404 — 1.4418 / X4CrNiMo16-5-1: https://www.bohler-edelstahl.com/en/products/n404/
• worldstainless, Martensitic Stainless Steels — grade correspondence table: https://www.worldstainless.org/Files/issf/non-image-files/PDF/ISSF_Martensitic_Stainless_Steels.pdf