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Surface Hardening: Nitrocarburizing vs. Carbonitriding

Jan. 19, 2022

Soft nitriding and carbonitriding are different heat treatment processes. Each process has its advantages, depending on the material used and the expected finished quality of the part.

Metallurgy is complex. However, it is valuable to explain the differences between these techniques and the benefits that result from their use. Induction hardening machine manufacturer shares with you,

Case hardening is the formation of a "shell" around the part receiving the hardening treatment. Both carburizing and carbo-nitriding harden the surface of the part by injecting carbon or carbon and nitrogen into the surface of the part. The material, part specification and intended use dictate that nitrocarburizing or carbonitriding is the best method of surface hardening.


In the carbonitriding process, the part is heated to the austenite range - approximately 1600°F (871°C) - in a sealed chamber prior to the addition of nitrogen and carbon. Nitrogen is added to low-carbon, low-alloy steels because they do not harden well without the push of nitrogen.


Compared to nitrocarburizing, carbonitriding typically achieves greater shell depth.

The carbonitriding process takes a few hours to a day or more to achieve the desired result: a part with a hard surface but a relatively ductile core.


Nitriding is used to harden the surface of parts made of relatively less expensive and easily machined steel, such as stamped automotive parts or wood screws. The process makes the part more resistant to wear and increases fatigue strength.

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Carburizing Nitriding

Nitriding also involves dissolving carbon and nitrogen into the workpiece, but more nitrogen is used in nitriding than in carburizing. Ferritic nitrocarburizing is unique in that it does not require heating the metal part to a phase change (975-1125°F). In this temperature range, nitrogen atoms are soluble in iron, but the risk of deformation is reduced.


The case depth after nitrocarburizing is usually shallow compared to carbonitriding. Nitriding reduces the likelihood of corrosion of the part and improves its appearance. The process typically takes only a few hours.


Parts improved by nitrocarburizing include drivetrain components for automobiles and heavy equipment, firearms components such as barrels and slides, and molds for manufacturing processes.

Nitriding and carbonitriding processes can be complex, but they are also critical to ensuring that parts can withstand the environment in which they are used. By learning more about these and other heat treating processes, you will save more money for your own production. Please contact us for more guidance.


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