Austenitic stainless steel

Expanite surface hardening can be applied to a variety of alloy materials and all main categories of stainless steel including austenitic:


UNS S30400 / S30403 / AISI 304 / 1.4301 / 1.4307

AISI 304 stainless has excellent fabricability and weldability characteristics and is the most widely used chromium-nickel austenitic stainless steel. It is nonmagnetic in the annealed condition and becomes slightly magnetic when cold worked. Nonhardenable by heat treating.

UNS S31600 / S31603 / AISI 316 / 316L / 1.4404 / 1.4435

AISI 316 stainless is a molybdenum-bearing austenitic stainless offering improved corrosion resistance in chlorides and many other environments over 304. It also has higher tensile and creep strength at elevated temperatures than the conventional 18% chromium - 8% nickel alloys. Suggested for applications requiring a moderate level of improvement in machinability for shorter runs of less complex parts, particularly at larger bar diameters.

UNS S30300 / AISI 303 / 1.4305

AISI 303 is an 18-8 chrome-nickel free-machining stainless steel with the addition of sulfur to enhance the machinability of this ordinarily tough and difficult to machine alloy. AISI 303 steel possesses nongalling properties that make disassembly of parts easy and help to avoid scratching or galling in moving parts. It is not recommended for vessels containing gases or liquids under high pressures.

The purpose of the process:


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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