Nitriding heat treatment: advantages and disadvantages

Nitriding treatment is a special type of heat treatment, thermochemical to be precise, which involves achieving surface hardening by introducing nitrogen into the surface layer of the material.

There are mainly two nitriding methods: gas nitriding and plasma nitriding.

In gaseous nitriding, the workpiece is placed in a sealed chamber containing a nitrogen-rich atmosphere, usually in the form of ammonia (NH3). The chamber is heated to a temperature of 450 to 600 degrees Celsius. The nitrogen diffuses into the surface of the material, reacting with alloying elements such as chromium, aluminum or molybdenum to form hard nitrides.

Plasma nitriding, on the other hand, uses a low-pressure plasma, composed of ionized gases, to introduce nitrogen into the surface of the material. The part is placed in a vacuum chamber and a voltage is applied to create the plasma. The nitrogen ions bombard the surface of the material, causing nitriding. This method offers greater control over the process, allowing complex shapes to be processed and the depth and properties of the nitrided layer to be precisely controlled.

Nitriding offers numerous advantages, making it a popular choice for improving the properties of metal components:

• Increased hardness: the formation of hard nitrides on the surface of the material significantly increases surface hardness, improving wear resistance and reducing surface deformation.
• Improved wear resistance: the nitrided layer offers increased resistance to wear, contact with abrasive or erosive environments, such as gears, bearings and cutting tools.
• Improved corrosion resistance: the nitride layer acts as a protective barrier against corrosive agents, such as oxygen and moisture, improving corrosion resistance.
• Absence of dimensional changes: being a low-temperature process compared to other heat treatments, nitriding causes minimal dimensional changes or distortions in treated components.
• Increased fatigue resistance: nitriding reduces the formation of micro-cracks on the surface, increasing fatigue resistance and improving component life under cyclic loads.
• Cost-effective process: nitriding can be more cost-effective than other surface hardening techniques because no further treatment is needed to achieve the required final hardness.

Despite its many advantages, nitriding also has some limitations and disadvantages:

• Limitations in material selection: nitriding is not suitable for all materials. Some metals, such as aluminum or titanium, cannot be treated with nitriding because of their chemical structure. This limits the choice of materials that can be used in this process.
• Surface treatment: as mentioned earlier, nitriding affects the surface layer of the material, with a limited depth of nitride. If a deeper hardened layer is needed, other processes such as carburizing may be more appropriate.
• Increased surface roughness: nitriding can slightly increase surface roughness due to nitrogen diffusion and nitride layer formation. In applications where low surface roughness is required, additional finishing treatments may be necessary.
• Limited repairability: If the nitrided surface is damaged or worn, repairing or repeating nitriding is complicated. It may be necessary to remove the existing nitride layer and repeat the whole process.

Nitriding treatment is an effective technique for improving the surface properties of metal components. Despite some drawbacks, nitriding remains a popular choice in industry to improve the performance of critical components, providing increased durability and reliability.

With the exception of the plasma nitriding method, we at UMBRAGROUP carry out the nitriding heat treatment, strengthened by 30 years of experience in the industry. We are able to meet the specific needs of our customers through rigorous in-house procedures, ensuring treatments that meet the most stringent industrial and aeronautical specifications.

Contact us now for more information!