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How plasma nitriding works

The nitriding process is a chemical heat treatment process that allows nitrogen atoms to penetrate into the surface of the workpiece at a certain temperature and in a certain medium. The nitriding process has the characteristics of low processing temperature and long process cycle. The hardened layer of the nitrided parts is shallow and the surface hardness is high. It is mainly used for parts with low load.

The main nitriding processes are gas nitriding and plasma nitriding. Both process methods use ammonia as the nitriding medium. During the nitriding process, the nitriding medium decomposes into active nitrogen atoms. The active nitrogen atoms are absorbed by the nitrided surface of the part. There is a concentration gradient between the nitrided surface of the part and the internal nitrogen element and diffusion occurs. process, the mechanism of nitriding process is the same.

Plasma nitriding, also known as plasma nitriding, plasma ion nitriding or glow discharge nitriding, is an industrialized surface hardening treatment process for metal materials. In plasma nitriding, the reactivity of the nitriding medium is not caused by temperature, but by the ionization state of the gas. In this technique, a strong electric field is used to create ionized molecules of a gas around a nitrided surface.

The advantages of plasma nitriding are related to the precise control of the nitriding microstructure, allowing the nitriding to form or not form a compound layer. Not only improves the performance of metal parts, but also extends their service life. The same goes for the strain limit and fatigue strength of the metal being processed. For example, the mechanical properties of austenitic stainless steels such as wear will be significantly reduced, and the surface hardness of tool steels will be doubled.

Because nitrogen ions are obtained through ionization, unlike gas or salt baths, plasma nitriding efficiency does not depend on temperature. Therefore, plasma nitriding can be performed over a wide temperature range from 260°C to over 600°C. For example, at moderate temperatures (such as 420°C), stainless steel can be nitrided without forming chromium nitride precipitates, thereby maintaining its corrosion resistance.