We tailor our process to your alloy and requirements

- The purpose of this process

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Logo - EXPANITE_HIGH-T - LOW RES - RGB

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 700HV on martensitic/ferritic grades.

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The purpose of this process is to dissolve nitrogen and carbon in the surface of stainless steel to a depth in the range of 5-45 µm. Peak hardness ranges from 1000-1200HV on austenitic grades to 1200-1800HV on martensitic/ferritic grades.

Logo - SUPER_EXPANITE - LOW RES - RGB

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 detph 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 processes 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.  

 

A gas process

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The benefits of a gaseous proces

The Expanite processes are gas processes. As a consequence, faults and small cavities are easily reached by the gasmolecules and hardened.

The processing is performed in retort furnaces with excellent gascirculation and temperature homogeneity - an extremely uniform hardening is achieved.

Effectively, even parts with high packing density can be treated as bulkware.

Taloring the profile

Carbon and nitrogen – a smooth profile

Smooth _hardness _profile

Double _layer

The dissolution of carbon and nitrogen is a key feature of the ExpaniteLow-T process. Nitrogen adds increased peak surface hardness while carbon bridges the gap to the relatively soft base material. The consequence is a smooth transition in hardness from the hardened zone to the base material, as illustrated in the composition/hardness profiles.

Gaseous surface hardening allows thermodynamically controlled formation of Expanite "layers" contrary to hitherto applied plasma and salt bath based methods. Consequently, tailoring of a combination of
individual carburizing and nitriding potentials is indeed possible, which implies large flexibility in tailoring the materials properties whether galling resistance or durability is required for.

The smooth composition profile is crucial for the enhancement of the load bearing capacity and fatigue strength.

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About surface hardening of stainless steel?