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Controlled gas nitriding and nitrocarburizing

Objective: Resistance to fatigue, wear, seizure and corrosion

In detail, nitriding is the diffusion of atomic nitrogen N onto the surface of previously hardened and tempered parts. This thermochemical process increases the surface hardness of ferrous materials, providing good resistance to abrasion, as well as increasing compressive stresses to improve fatigue strength. Nitrocarburizing, on the other hand, is a treatment derived from nitriding, in which carbon is added to nitrogen diffusion, increasing the wear and friction resistance of the steel. The insertion of nitrogen N (or N and C in the case of nitrocarburizing) and the formation of nitrides with the steel's alloying elements result in surface hardening, providing the desired properties (hardness of 750 to 1100 HV).

Treatment between 500 and 570°C greatly reduces the risk of deformation.

employee loading a gas nitriding furnace

Our process

Furnaces used for controlled gas nitriding are generally cylindrical, such as pot, shaft or horizontal furnaces. These furnaces can reach very large dimensions to accommodate various types of parts and materials, including stainless steel.

01

Oven preparation

Before the start of the treatment process, the furnace is purged of any residues or impurities, then heated to the optimum treatment temperature. This preparatory step is essential to maintain a controlled, neutral atmosphere for uniform heat treatment.

02

Gas injection

The active gas mixture, consisting of ammonia (NH3) or a mixture of NH3 and fuel gas, is injected into the furnace. This gas is maintained at a given temperature for a certain period of time to obtain the desired layer depth. The nature and depth of the nitrided layer depend on the steel grade used, the treatment time and temperature, and the composition of the nitrogen-rich treatment atmosphere.

03

Composition of the nitrided layer

The structure of the nitrided layer is composed of :

- A combination layer of 5 to 25 microns, where nitrogen is combined in the form of iron nitrides (Gamma Prime and/or Epsilon). This surface layer significantly increases wear and corrosion resistance. It offers the possibility of creating a porous layer on the extreme surface to enhance mechanical resistance performance (THERMI-NITROX®).

- A diffusion layer of 0.1 to 1 mm, depending on steel grade and treatment time. This diffusion layer helps improve fatigue and abrasion resistance, bringing high strength and extended service life to the treated part.

04

Oven control

For complete control of the nitrided layer, in terms of both chemical composition and morphology, our process is fully automated, with hydrogen probes for continuous measurement and regulation of the nitrogen potential (Kn) and oxygen probes for continuous measurement and regulation of the carbon potential (Kc).

    Features and benefits of controlled gas nitriding

    In general, nitriding provides parts with wear and seizure resistance, fatigue strength and low deformation, making it possible to process finished parts. Controlled gas nitriding brings additional benefits, particularly in the automotive and aerospace sectors where precision and durability are crucial:

    Mastery

    Computerized process management enables precise control of the chemical composition and depth of the combination layer (Gamma Prime and/or Epsilon), guaranteeing homogeneous application and a significant improvement in surface hardness and corrosion resistance. This approach also helps to adjust parameters according to the specific needs of the materials being treated, such as steel or stainless steel.

    Uniformity

    The process ensures very good treatment uniformity, even for parts with complex shapes. This method helps to achieve a high level of hardness across the entire surface of your metal.

    Competitiveness

    The ability to maintain a high loading density in the furnace leads to a significant reduction in cost, making heat treatment more competitive with other methods such as ion nitriding. Process efficiency is enhanced by optimized treatment cycles for high-quality results.

    Depth

    Advanced technology enables the creation of deep layers, offering enhanced protection against fatigue, abrasion and wear, under favorable economic conditions. This process can be particularly beneficial for parts subject to high mechanical stress.

    Adaptability

    Thanks to the use of modern technologies, controlled gas nitriding can be applied to large parts such as gears and tooling, requiring high precision and resistance to temperature variations and friction effects.

    Further information on controlled gas nitriding

    Controlled gas nitriding is carried out in a forced convection furnace, using a mixture or active gas at close to atmospheric pressure, often in a low-temperature environment to minimize the risk of deformation. The active species, atomic nitrogen N, or in the case of nitrocarburizing N and C, are obtained by cracking ammonia NH3 (or NH3 with added fuel gas for nitrocarburizing) at the process temperature (500 to 570°C).Nitrogen and/or carbon enrichment is automatically regulated using specific sensors (hydrogen probe and oxygen probe), feeding an algorithm for calculating nitriding potential (KN) and/or carbon potential (KC), to guarantee optimum quality and maximum surface cleanliness.

    composition controlled gas nitriding

    For study and order

    Information to be communicated :

    - Drawing of the part (with areas to be protected if necessary).
    - Number of parts per shipment per year.
    - Type of steel: standard (or commercial) designation.
    - Specification of the layers to be produced (with machining allowance - if necessary).
    - Previous treatments (pretreated, tempered, stabilized, annealed).

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    business sectors concerned

    Typical applications: extrusion screws and sleeves, forging tools, deep drawing, cams, slides, gears, mechanical friction parts.

    Aerospace
    Aerospace market
    Automotive
    Automotive market
    Rail energy
    Rail energy market
    Machines and components
    Machinery and components market
    Medical
    Medical market
    Tools
    Tools market
    Sports and leisure
    Sports and leisure market
    Public works
    Public works contract

      Our various documentations

      Heat treatment white paper
      Thermilyon Group white paper on metal heat treatmentRead more
      Controlled gas nitriding and nitrocarburizing
      loading a nitrex nitriding furnace at Thermi-PicardieRead more
      See all our documentation

      Our FAQs

      What is vacuum deposition?

      Vacuum deposition is a surface treatment used to deposit a material or alloy on a mechanical part.

      The use of vacuum technology ensures a perfectly clean, non-polluting process.

      It is not subject to REACH legislation.

      What are the advantages of PVD technology?

      This process greatly increases resistance to wear, abrasion, friction and corrosion. As a result, component life is greatly extended.

      Standard thicknesses are of the order of 3µm and deposition is carried out on finished parts.

      What's the difference between PVD and PACVD?

      PVD is physical vapor deposition. The element to be deposited is obtained by evaporation or sputtering via a physical process. PACVD is plasma-assisted chemical vapor deposition. The element to be deposited is obtained from chemical reactions. Plasma enables this chemical reaction to take place at lower temperatures.

      What are the industrial applications of vacuum deposition?

      Vacuum deposits are classified into several categories: anti-wear, friction, decorative and biocompatibility. The applications are therefore very varied: automotive components, aerospace, tooling, cutting tools, medical devices, decorative parts...

      How do I choose the right deposit method?

      The deposition method depends above all on the nature of the coating to be deposited and the substrate.

      If the substrate cannot be heated to high temperature, the deposition must be carried out using low-temperature technology.

      If the coating to be deposited consists of a solid element (metal or graphite target), a physical process such as PVD is used. If the coating consists of a gas or liquid, a chemical process such as CVD or PACVD is used.

      What is the purpose of case-hardening? 

      Incorporate carbon below the surface of the steel part to improve fatigue and wear resistance on the surface, while maintaining good core mechanical properties.

      See all FAQs

      Do you have a question or a need?

      Our dedicated team will advise you on the process best suited to your needs.

      Contact us

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