Duplex

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

 

UNS S31803 / S32205 / AISI 318LN / 1.4462 / Alloy 2205

Alloy 2205 offers an excellent combination of strength and corrosion resistance due to its chemical composition and duplex microstructure consisting of austenite and ferrite phases. Duplex stainless steel has twice the annealed yield strength of typical austenitic stainless steels. In the hot rolled unannealed condition, a yield strength of 75 ksi (518 MPa) or higher can be achieved for bar diameters up to 1.375 in. (34.925mm). Duplex possesses good resistance to general corrosion in many acid environments and, has excellent resistance to chloride stress corrosion cracking, pitting and crevice corrosion

UNS S32750 / AISI F53 / 1.4410 / Alloy 2507

Alloy 2507 is a super-duplex stainless steel with a microstructure consisting of austenite and ferrite phases in approximately equal amounts. The chemical composition and microstructure impart a good combination of strength, corrosion resistance and toughness with an annealed yield strength twice that of typical austenitic stainless steels possessing comparable impact strength. AISI F53 exhibits good resistance to general corrosion in many acid environments with exceptional resistance to chloride stress corrosion cracking, pitting and crevice corrosion.

 

The purpose of the process:

ExpaniteHigh-T

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.

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.

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.

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