improves the corrosion resistance of alloys
what is Nitrotec®?
Nitrotec® (nitriding-oxidising-protection) is a patented thermo-chemical diffusion process, during which the surface of steels is nitrocarburized and next oxidized, cooled and – if requested – sealed. Nitrotec® combines the useful properties of the nitrocarburizing (improved surface hardness and wear resistance, enhanced fatigue strength, nihil distortion) with the high resistance against atmospheric corrosion, increased yield strength and an attractive black finish.
Nitrotec®-layers are created in nitrogen and carbon submitting gaseous atmospheres at temperatures between 540-740⁰C. The treatment generates compound layers, supported by nitrogen rich diffusion zones in the base material. The choice of process temperature, time and nitrogen potential of the atmosphere in relation to the type of steel, controls the structure, composition and hardness of the compound layer and the diffusion zone underneath. The innovative oxidation technique and the special water based quenchants, as well as the organic sealing are based on the technical demands for the application.
At the surface an iron oxide layer (Fe3O4) is formed for improvement of the corrosion resistance of the material. Underneath the oxide layer a compound layer is present, which consists of iron nitrides, iron carbides and nitrides or carbonitrides of the alloying elements. At process temperatures above 590⁰C, a nitrogen-rich austenite layer is formed between the compound layer and diffusion zone. The transition to the core is formed by the diffusion zone, which consist of iron (ferrite)matrix, supersaturated with nitrogen and possibly precipitated nitrides.
In common with other low temperature surface treatments, Nitrotec® does not introduce distortion into the part, this means that components can be used and fitted directly after treatment.
The conventional Nitrotec® has a pleasing black appearance and vastly superior corrosion resistance to zinc plating. These low temperature diffusion treatments make low alloy and mild steels up to four times stronger, produce wear resistance equal to hard chromium plating and result in a black finish that has outstanding resistance to corrosion.
An important member of the family of Nitrotec® treatments is NITROTEC®-S, a multi-stage process, where parts are first machined to a final surface finish, Nitrotec® treated, surface polished in a controlled manner, followed by a post oxidizing treatment. This finish gives a dramatic improvement in frictional characteristics and corrosion resistance properties, superior to those obtained when using hard chromium plating techniques.
benefits of Nitrotec®
The surface hardness as well as the specific hardness profiles indicate the capability of Nitrotec treated components to resist indentation from point contact surface loading.
When rapidly cooled after Nitrotec treatment, significant strengthening of thin sections, as for example sheet metal, occurs. This results in an increase in both yield strength of the base material and its fatigue strength.
Nitrotec combined with an organic sealant retained in the micro porous layer, imparts corrosion resistance superior to that of electro plated components, and comparable to that of medium grades of stainless steels. A combination of Nitrotec finishes with a range of organic sealants give salt corrosion resistance with a minimum of 240 hours.
Nitrotec treatments, that are environmentally friendly and clean, ensure that good surface finishes can be maintained.
Nitrotec treatment produces an aesthetically pleasing black/anthracite surface finish.
Traditional hardening practices may give rise to distortion and poor dimensional control, because metallurgical phase changes when rapidly quenching from high treatment temperatures. During Nitrotec treatment these changes do not occur, therefore allowing the treatment of close-tolerance precision parts, especially thin section components.
The layer which is formed during Nitrotec consists of compound zone which is supported by a nitrogen-austenite layer. The oxide, so-called magnetite, is about 1 μm in thickness and can be increased up to 4 μm when applicable. Also, the thickness of the compound layer is variable pending on the material and the application. Underneath the nitrogen-austenite, the so-called diffusion zone is created.
fields of application
The types of components that are treated with Nitrotec® include: Pistons, Ball Studs and Other Mild Steel Components.
Nitrotec® is a replacement for chromium plating. It is more environmentally friendly and delivers heat treatment of steels and alloys very successfully.
Improvements in performance can significantly reduce the manufacturing and material cost of components, a fact proved repeatedly by the automotive industry as they use treated pressed parts.
groundbreaking industries we serve
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