Martensitic Stainless Steel

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. Learn more on WIKI 

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 / 1.4040

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.

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 EN AISI
 X12Cr13     1.4006      410
 X20Cr13     1.4021  420
X50CrMoV15  1.4116  
X39CrMo17-1  1.4122  
X105CrMo17  1.4125 440C
X17CrNi16-2  1.4057 431
X3CrNiMo13-4  1.4313  
X4CrNiMo16-5-1  1.4418  
X5CrNiCuNb16-4  1.4542 630


The purpose of this process is to dissolve nitrogen in the surface of stainless steel to a depth in the range of 0.2-2 mm. Peak hardness ranges from 280HV on austenitic grades to 950HV on martensitic/ferritic grades.


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. 


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.


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