Stainihard® for surface hardness of stainless steel

what is Stainihard®?

Stainihard® NC is a process to harden the surface of (austenitic and duplex) stainless steel, without having a negative effect on its corrosion resistance. In some cases, this is even improved.

The treatment is based on the classic nitro-carburization in gas. Stainihard® NC is a variation, which makes it possible to apply this process to stainless steel. As with other diffusion processes, products can be treated as single work pieces as well as in bulk.

With Stainihard® NC the surface is enriched with nitrogen and carbon to improve the mechanical properties of the product.

Stainihard® NC is a registered trade mark of Aalberts surface technologies Eindhoven B.V.

the process

Depending on the application, there are various process options, with the aim of achieving the desired properties.

During the Stainihard® process the surface will be enriched with nitrogen and carbon in a special way. With austenitic stainless steel this is not easily possible. Nitrogen and carbon diffuse at a low temperature (<450°C) in the product surface. The result is a very high surface hardness (1200-1400HV0.05) without negatively affecting the corrosion resistance!

The Stainihard® layer is an expanded austenite zone (also called S-phase). This zone consists of the relevant stainless-steel material with a supersaturation of nitrogen and carbon. Because of this supersaturation, compressive stresses arise. This increases the hardness considerably, without negatively affecting the corrosion resistance. The reason is, with Stainihard® NC the formation of chromium nitride (CrN) and / or chromium carbide (CrC) is suppressed (expanded austenite). This in contrast to the classical nitriding processes such as salt bath and plasma nitriding, where the corrosion resistance will decrease considerably as a result of the formation of this chromium nitride and carbides!

The depth of this expanded austenite layer formed by Stainhard is partly dependent on the chosen stainless-steel material, the deformation degree and the surface condition.

fields of application

Stainihard® NC is a process to harden the surface of (austenitic and duplex) stainless steel.

The properties of the process are

High surface hardness
High abrasion resistance against abrasive wear
High resistance against cold welding, seizing or contact corrosion
Corrosion resistance is not affected, in some cases even improved
High resistance to shear
No change in appearance
Lower friction coefficient
Higher fatigue strength
Good dimensional and shape stability

The Hardness of Stainihard® is 1200-1500HV0,01.

The above hardness refers to the hardness on the surface if it is measured in a cross-section of the layer. Regular hardness measured on the surface is: 1000-1400HV0.05 at a depth of 10 to 30 µm.

The hardening depth of Stainihard® NC depends on the type of stainless steel, the surface condition and the degree of deformation. With increasing surface deformation, the layer depth decreases.