When and Why Ion Nitriding/Nitrocarburizing Makes Good Sense

Advanced Heat Treat staff Dr. Edward Roliński and Gary Sharp authored this article from Industrial Heating magazine, August 11, 2005:

     “Ion nitriding can be used in many applications, but some are so unique that they can be called “the best” applications, where the competitive treatments such as salt bath and gas nitriding cannot easily duplicate the unique results of ion nitriding.

Ion, or plasma, nitriding has been studied and used industrially for more than 40 years [1-8], but the technology has not been used to its full potential. Ion nitriding/nitrocarburizing is a low temperature (800-1100˚F, or 430-595˚C) process, which results in little or no distortion of the treated parts even if significant residual compressive stress is induced to the surface layer of the treated products. The ion nitriding process also has been referred to by other surface treating characteristics including plasma, vacuum, diffusion, low nitriding potential, passive surfaces activating, easy-to-control structure and pollution-free processes. These process characteristics with the exception of the low nitriding potential concept are discussed in the literature.”

Click here to read the entire article:

http://www.industrialheating.com/Articles/Feature_Article/f022e50797cb7010VgnVCM100000f932a8c0

Learn more about the authors here www.ahtweb.com

Nitriding and Nitrocarburizing

Nitriding and Nitrocarburizing are performed at lower temperatures than conventional heat treatments, which minimizes distortion.

These heat treatments improve wear resistance, fatigue strength, and corrosion resistance.

Nitriding/Nitrocarburizing Types:

• Ion Nitriding (Plasma Nitriding / Nitrocarburizing)
• Gas Nitriding (Gaseous Nitrocarburizing)
• Salt-Bath Nitriding (Liquid)

Photo of Ion Nitriding:

For more information on these heat treatments, visit www.ahtweb.com

Case Depth Terms

When applying a heat treatment, such as ion nitriding, to a part, it is important to know the following case depth terms:

Effective Case Depth (ECD):

The distance from the surface of a hardened case where a specified level of hardness is maintained (typically 50 HRC eqv.).

Total Case Depth (TCD):

The distance from the surface of a hardened case to a point where differences in physical properties of the case and core are no longer distinguished (visual or hardness method).

For example:

 For more information, visit www.ahtweb.com.

Ion Nitriding Frequently Asked Questions

Will my part have any growth and/or shrinkage from UltraGlow® Ion Nitriding?

Generally, your parts will have minor growth depending on the process that you are requesting. The growth will be dependent on the amount of compound zone (white layer) that is required/achieved during processing. The standard rule of thumb is ~70% of the CZ Layer thickness.

How does AHT know that my parts met the right hardness and case depth specified?

When processing your parts, an AHT sample of similar material and/or customer supplied sample will be processed with the parts. After processing, a full metallurgical evaluation will be performed in order to document the results achieved.

What will happen to parts that I have repair welded?

The weld repair should nitride dependent on the material. If you have made weld repairs, it is imperative that you provide the welding material to AHT prior to processing as it may respond different to nitriding than the base material(s).

I have heard of UltraGlow® Ion Nitriding but do not know exactly what it is?

The process is conducted in a vacuum chamber back-filled to a very low pressure with a mixture of nitrogen and other gases. A high voltage electrical charge forms plasma from the gas mixture. Nitrogen ions then accelerate through the plasma and impinge on the workpiece. The ion-bombardment process heats the workpiece, cleans its surface, and results in absorption of active nitrogen into the surface of the material producing a “hardened case”.

How long does UltraGlow® Ion (Pulse Plasma) Nitriding take?

Due to the various materials and/or requirements the UltraGlow® Ion (Pulse Plasma) Nitriding process can take anywhere from a few hours up to a few days.

What do I need to do to my parts after UltraGlow® Ion Nitriding?

UltraGlow® Ion (Pulse Plasma) Nitriding is generally performed on “finished” machined parts. After processing, a light polishing of the part(s), if required, will bring your part back to the required surface finish with no affect to the nitrides.

What information do you need before you can quote/process my parts?

At a minimum, we need the following information:
• Material/Steel number
• Type of heat treat requested
• Surface hardness
• Case depth
You may also include the following additional information:
• Core hardness
• Selective location for heat treat
• Any previous heat treat/thermal processing on parts

When is carbonitriding better than carburizing?

Carbonitriding (CN) is a very effective case hardening process, and it can be used on a variety of low carbon steels. CN is well suited for sheet steel and 10xx, 11xx, and 12xx series steels. The addition of nitrogen to the case hardening process allows the case hardened layer to react and form a harder case than would typically be provided with carburizing alone. The CN is also a lower temperature process, which can contribute to lower distortion.