gas nitriding
gas nitriding: nitriding of steel
Gas nitriding is a thermochemical surface treatment applied to steel with the aim of hardening the surface to significantly improve wear resistance, corrosion resistance, and fatigue strength. Gas nitriding is particularly suitable for products exposed to high surface loads. Localized treatment is also possible. The process takes place at a relatively low temperature, which often eliminates the need for further machining in many applications. There are various nitriding processes to create a hard, wear-resistant layer on steel. Gas nitriding is one of them, but there are alternatives as well.
gas nitriding process
Gas nitriding is a process in which nitrogen is introduced into the surface of steel by diffusion. This is done in a furnace by heating (at temperatures between 475°C and 550°C) under an atmosphere containing ammonia gas (NH₃).
The material is then held at this temperature for a certain period, which can range from a few hours up to 120 hours. The resulting nitrided layer in the metal lattice is a compound of nitrogen atoms with iron and the alloying elements present. The desired hardness is determined by the chosen material type and the extent to which these so-called nitrides can be formed.
A so-called nitrided layer is formed, consisting of a compound layer (also called the white layer), which is very hard (but can also be somewhat brittle), and a diffusion zone. This zone is slightly lower in hardness but provides strength and supports the compound layer. The surface can reach hardness values up to 1200 HV1. The achievable nitriding depths depend not only on the chosen nitriding process but also on the material. Typically, depths can range from 0.1 to 0.8 mm.
The desired hardness is created by the transfer of nitrides into the metal mesh. Different degrees of hardness can be achieved depending on the element used.
application areas
Examples of components commonly chosen for gas nitriding:
- Shafts: Gas nitriding is often used for surface hardening various types of shafts, especially those that must withstand high loads, such as drive shafts in the automotive industry.
- Gears: Gears are often nitrided to improve their wear resistance and durability, especially those in gearboxes exposed to high loads and friction.
- Tool Steel: Tools such as molds, dies, and cutting tools can gain increased hardness and wear resistance through gas nitriding, extending their lifespan and improving the quality of machined workpieces.
- Crankshafts: Crankshafts in combustion engines are often nitrided to increase surface hardness and thus extend engine life.
- Piston Rods: Gas nitriding is also used on piston rods to increase surface hardness and reduce wear.
application of gas nitriding in various industries
The use of gas-nitrided components is found in many different industries. Some examples include:
- In the automotive industry, gas nitriding optimizes the wear resistance of drive shafts, transmission components, and crankshafts, resulting in a noticeably longer lifespan of the components.
- In the tooling industry, gas nitriding enables the production of extremely robust and wear-resistant tools such as molds, dies, and cutting tools.
- In the aerospace industry, nitriding is used to increase the surface hardness of components such as piston rods and pistons, improving their performance under extreme conditions.
advantages of gas nitriding
Gas nitriding significantly increases the performance, reliability, and lifespan of components. Some advantages include:
- Higher bending and fatigue strength
- Improved wear and abrasion resistance
- Lower coefficient of friction
- High temperature resistance
- Reliably reproducible results
- Partial treatment is possible
- Low-temperature process, minimal distortion, saves post-processing
- Environmentally friendly compared to other processes (e.g., chrome plating)
suitable metals and results for the nitriding process
When is a material suitable for nitriding?
In principle, any type of steel can be nitrided. However, to achieve seriously high hardness, it must be alloyed with elements that promote nitrogen absorption, such as:
- Chromium
- Vanadium
- Molybdenum
- Titanium
- Aluminum
These elements ensure the formation of hard to extra-hard nitrides on the surface. Furthermore, depending on the application, it is important that the core remains tough, but sometimes a certain pre-applied hardness/strength is needed to prevent deformation under load. Pre-stress relieving can ensure the material is stress-free, reducing the risk of shape changes.
Note: Highly alloyed materials with high chromium (Cr) and nickel (Ni) content, such as titanium, stainless steel (RVS), or Ni-based alloys, are not suitable for gas nitriding. For these materials, alternative processes such as plasma nitriding or the specialized Stainihard® process should be chosen.
certifications
Certified according to:
- DIN EN ISO 9001:2015
- VDA 6.1:2016
- ISO 13485:2016
environment, sustainability, and safety
Aalberts surface technologies strives to produce as environmentally and eco-friendly as possible. Gas nitriding is also an environmentally friendly process, and products last longer, meaning they need to be replaced less often. We are proud to have received the EcoVadis Medal, which confirms our commitment to responsibility for people, the environment, and our customers and suppliers throughout the value chain.
frequently asked questions – gas nitriding
What is gas nitriding?
Gas nitriding is a thermochemical surface treatment applied to steel to harden the surface and significantly improve wear resistance, corrosion resistance, and fatigue strength.
Which steels are suitable for gas nitriding?
Many types of steel are suitable for nitriding. The best results are achieved with so-called nitriding steel with a carbon content between 0.3 and 0.4% and a certain proportion of alloying elements: aluminum and chromium.
Are there alternative methods for surface hardening steel?
Yes, these include case hardening (also called carburizing) and induction hardening.
Are there limitations to gas nitriding?
The achievable nitriding depth is limited to a maximum of 0.6–0.8 mm, whereas carburizing treatments can create significantly deeper layers. Furthermore, highly alloyed steels cannot be nitrided; these can be treated with plasma nitriding or the Stainihard® process.
How long does the gas nitriding process take?
Depending on the material and the desired nitriding depth, between 4 and 100 hours.
industries we serve
process locations
Any questions? Contact us directly or select a process location near you.
Amboise
France 47.41544421.0245775 info.amboise@aalberts-st.com +33 247 2374 74 show locationDunningen
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Germany 49.01621959.7588191 info.gaildorf@aalberts-st.com +49 7971 96980 show locationKehl
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