Martensitic Stainless Steel hardening

Expanite Surface Hardening For a Variety of Stainless Steel Alloys Including Martensitic

Martensitic stainless steel is on of the major categories of stainless steel include austenitic, ferritic, duplex, and precipitation hardened variants

Martensitic stainless steel is a stainless steel alloy characterized by its martensitic crystal structure, which can be strengthened and refined through processes such as aging and heat treatment.

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UNS S42010 / AISI 420 / 1.4021

AISI 420 is martensitic stainless steel specially designed for applications requiring high mechanical properties combined with improved corrosion resistance relative to traditional martensitic steels. Ideal for applications requiring high strength, high hardness, and corrosion resistance similar to AISI 304/ 1.4301 stainless.

UNS S44002 / AISI 440A / 1.4109

AISI 440A is a high-carbon high-chromium martensitic stainless steel designed to provide stainless properties with excellent hardness. The alloy has an excellent combination of strength, ductility, toughness, corrosion resistance, and workability. It attains a hardness of 56 HRC and maximum toughness when heat treated and has good toughness at cryogenic temperatures and relatively high tensile and yield strengths at moderately high elevated temperatures. These properties further increase.

UNS S17400 / AISI 630 / 1.4542 / 17-4PH

SAE Type 630 stainless steel (more commonly known as 17-4 PH, or simply 17-4; also known as UNS S17400) is a grade of martensitic precipitation hardened stainless steel. The corrosion resistance and machinability of 17-4 are comparable to austenitic 304 stainless steel. 17-4 is magnetic due to its martensitic structure. Overaging (aging beyond the peak strength condition) improves resistance to stress corrosion cracking.

Properties of Martensitic Stainless Steels:

Martensitic can be hardened through heat treatment, typically achieved by either quenching and stress relieving or quenching and tempering processes. The specific composition of the alloy, combined with the rapid cooling during quenching, facilitates the formation of martensite.

Un-tempered martensite, however, tends to be low in toughness and consequently brittle. On the other hand, tempered martensite provides steel with a desirable balance of hardness and toughness, which is particularly advantageous in applications such as medical tools (including scalpels, razors, and internal clamps).

EN designation	Euronorm (EN) number	AISI grade
X12Cr13	1.4006	410
X20Cr13	1.4021	420
X50CrMoV15	1.4116
X39CrMo17-1	1.4122	303
X105CrMo17	1.4125	440C
X17CrNi16-2	1.4057	431
X3CrNiMo13-4	1.4313
X4CrNiMo16-5-1	1.4418	S165M
X5CrNiCuNb16-4	1.4542	630/17-4PH

ExpaniteHigh-T

The purpose of this process is to dissolve nitrogen in the surface of stainless steel to a depth of 1mm. Peak hardness ranges from 280HV on austenitic grades to 950HV on martensitic/ferritic grades.

ExpaniteLow-T

The purpose of this process is to dissolve nitrogen and carbon in the surface of stainless steel to a depth in the range of 5-30µm. Peak hardness ranges from 1100-1300HV on all grades.

SuperExpanite®

The purpose of this process is to combine ExpaniteHigh-T and ExpaniteLow-T processes to achieve higher load bearing and corrosion properties. Firstly, the ExpaniteHigh-T process is applied to create a deep case depth with moderate nitrogen content. Secondly, the ExpaniteLow-T process is applied to create a high-hardness surface on top of the ExpaniteHigh-T zone. The Expanite process does not result in a coating, but a diffusion zone with an increased carbon and nitrogen content. We call this zone expanded austenite, expanded martensite or simply: Expanite.

Discover More Stainless Steel Solutions with Expanite

Expanite® surface hardening and heat treatment solutions unlock the full potential of martensitic stainless steels by improving wear resistance, eliminating galling, and extending component lifetime without compromising corrosion resistance. With our proven expertise, we help customers in demanding industries achieve superior performance and reliability.

To gain a complete overview of how Expanite can support your material choices, we also invite you to explore our dedicated pages on Duplex, Ferritic, and Austenitic stainless steels – and discover how our technology adds value across the full range of stainless steel alloys.

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