Home Ion nitriding

Heat treatment and ion nitriding

Objective: Resistance to fatigue, wear and seizure

Nitriding is a thermochemical treatment involving the diffusion of atomic nitrogen N onto the surface of steel parts previously hardened and tempered. 

The insertion of nitrogen N into the steel (or N and C for nitrocarburizing treatment) and the formation of nitrides with the steel's alloying elements cause surface hardening. This transformation results in a high-quality nitrided layer, offering a hardness of between 750 and 1100 HV, particularly suited to industrial applications where fatigue and wear resistance are crucial.

Ion nitriding, in particular, uses a process where nitrogen ions are accelerated and bombard the metal surface in a vacuum or gaseous environment, carried out at a controlled treatment temperature. This process achieves greater diffusion layer uniformity through improved ion etching and optimized layer thickness for each specific application. Advantages include a significant improvement in the mechanical strength and durability of treated parts, making this technique particularly popular in most mechanical engineering sectors.

This technology is particularly well-suited when process savings are required.

The ion nitriding process at Thermi Lyon

Ion nitriding is carried out in a vacuum furnace using a controlled flow of active gases, dissociated by plasma.

Vacuuming the oven chamber

Beforehand, the parts are carefully washed in dedicated machines. Ion nitriding is carried out in a vacuum furnace in an air-free environment to avoid contamination by external elements such as oxygen. This preliminary step ensures that the environment remains neutral and conducive to top-quality nitriding.

Gas injection

Injection of the active gas mixture, under reduced pressure, is carefully controlled to maintain optimum mass flow. These gases, often a mixture of nitrogen or hydrogen, are used to facilitate the formation of atomic nitrogen on the metal surface.

Plasma creation

By creating a plasma ionizing the furnace atmosphere, nitrogen ions are generated, helping to pickle and heat parts. Modern furnaces, often equipped with additional heating by resistors or active grids, optimize this process to reach the required temperatures without overheating the material.

The nitrided layer comprises :

- on the surface, a combination layer, often referred to as the white layer, from 5 to 25 µm in thickness, in which the nitrogen is combined in the form of iron nitride (γ, ε or γ +ε), conferring very high hardness. This layer promotes sliding, thus increasing resistance to wear and seizure.

- an underlying diffusion layer, generally between 0.1 and 0.5 mm deep, which ensures good fatigue resistance and also enhances wear resistance. The composition and thickness of this layer depend on the steel grade and the specific treatment parameters used.

Cooling

At the end of the diffusion cycle, cooling is achieved by forced circulation of neutral gas, such as nitrogen, to ensure uniform, controlled cooling. All treatment parameters, including temperature, time, mass flow rates and plasma characteristics, are rigorously managed by an advanced computer system.

    Features and benefits of ion nitriding

    Ion nitriding offers numerous advantages for all types of steel and stainless steel parts, particularly those subject to wear, seizure and fatigue.

    fatigue resistance

    Improved surface hardness

    For parts subject to high mechanical stress, nitriding is a recommended heat treatment. This process improves surface hardness and corrosion resistance, in the case of post-oxidation, while extending the service life of treated materials.

    limited deformations

    Low processing temperature

    Thanks to the moderate treatment temperature of around 500°C, part deformation is minimized, which is crucial for maintaining the precise geometry of your components. This level of control is particularly important for parts made of stainless steel and other special alloys.

    processing on finished parts

    No re-machining required

    Ion nitriding can be carried out on parts in the hardened-tempered state, at final dimension, or with a small grinding allowance. This feature makes ion nitriding ideal for final applications where dimensional accuracy is critical. In some cases, it may be necessary to first stabilize the blank or allow for a slight machining allowance.

    Versatility

    Choosing the right steel grade

    Ion nitriding can be applied to all steel grades, including stainless steels, offering a solution for a wide range of industrial needs. This method is suitable for a variety of applications without compromising essential mechanical properties.

    savings

    Localized treatment possible

    The ease and reliability of metal shielding during ion nitriding means that specific areas are effectively protected from nitriding, ensuring that only the desired surfaces are treated. This technique is particularly useful for complex parts where certain areas must remain untreated for functional or assembly reasons.

    Information for study and order

    - Drawing of the part (possibly including: area to be protected).
    - 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 any).
    - Previous treatments (pre-treated, quenched and tempered, stabilized, annealed).

    Ask for a quote

    business sectors concerned

    Typical applications: cams, extrusion screws, tooling, slides, gears and all stainless steel parts

    Our various documentations

    Heat treatment white paper

    The ion nitriding process

    See all our documentation

    Our FAQs

    Why nitriding/nitrocarburizing?

    Diffusion of nitrogen on the surface of the part to considerably improve mechanical strength and wear resistance on the surface, while maintaining good core strength. This treatment greatly improves wear resistance, but as the temperature is low (500°C), it causes very little deformation and can be applied to a finished part.

    How is heat treatment carried out? 

    Heat treatment is carried out using furnaces. There are air, atmosphere, vacuum, plasma and induction furnaces.

    What are the main types of heat treatment?

    There are two main types: softening treatments to improve the shaping or machining of parts, modify or improve the metallurgical structure or defragilize certain mechanisms. Hardening treatments in the mass or on the surface to improve the mechanical performance of components.

    What do I need to know when requesting or placing an order for heat treatment?

    Type of steel, desired steel characteristics (hardness), quantity of parts per shipment and per year, part drawings and specifications. If possible, the operating mode of the part and its final use.

    See all FAQs

    Do you have a question or a need?

    Our dedicated team can handle any ion nitriding project.

    Contact us

    Our latest news

    Discover Thermilyon Group news and our best articles on heat treatment.

    press-hardened part
    Focus on press hardening and its advantages
    Press-hardening serves a very specific purpose: to prevent part deformation during the rapid cooling phase induced by quenching. This method improves the performance of steels by giving them a martensitic structure, without the need for reworking. Designed for large production runs of parts with complex geometries, [...]
    January 30, 2025
    Focus on press hardening and its advantages
    martensitic-hardened metal parts
    Focus on martensitic hardening and its advantages
    The aim of martensitic hardening is to bring out a specific constituent in steels, called martensite, to make them harder and more resistant to wear and mechanical stress. It is one of the oldest known heat treatments of metals, and is still used today, thanks to its effectiveness and the [...].
    January 30, 2025
    Focus on martensitic hardening and its advantages
    heat-treated stainless steel tanks
    Thermochemical treatments for austenitic stainless steels
    Stainless steels are metals renowned for their anti-corrosion properties. Since its creation, THERMI-LYON has been offering its customers a range of thermochemical treatment solutions for austenitic stainless steels on a subcontracting basis. Over 60 years' experience in the treatment of stainless steels [...]
    December 19, 2024
    Thermochemical treatments for austenitic stainless steels
    Steel bars of various sizes, illustrating annealing and tempering processes
    Annealing and tempering: what are the differences and what are the different types of annealing?
    Annealing and tempering are among the heat treatment techniques applied mainly to steels (copper alloys, aluminum and titanium too). Both methods involve heating parts to precise temperatures, which vary according to the process, but do not serve the same purpose. There are two main types of annealing [...].
    December 10, 2024
    Annealing and tempering: what are the differences and what are the different types of annealing?
    stepped quenching diagram
    A closer look at step quenching and its advantages
    Staged quenching is based on cooling in stages. It includes a traditional initial heating phase, to reach a given temperature, but requires controlled cooling to be divided into several stages. This process offers a number of advantages, including a reduced risk of breakage or deformation, compared to quenching with [...].
    November 18, 2024
    A closer look at step quenching and its advantages
    Bonded varnish Complementary treatment to heat treatment
    Why choose glide varnish as a complementary treatment?
    Bonded coatings are an excellent way of improving the coefficient of friction of metal parts. Applied, possibly following a heat treatment operation, it ensures that the parts slide better together and reduces the risk of seizing. This technology is used particularly in the construction and screw industries, but also in the [...]
    November 18, 2024
    Why choose glide varnish as a complementary treatment?