The nitriding process is a chemical heat treatment technique that penetrates the nitrogen atoms into the surface layer by heating the workpiece in a nitrogen-containing medium, aiming to improve the surface properties of the material.

Common methods of nitriding

Gas nitride, ion nitride, nitrogen and carbon co-infiltration.

gas nitriding

There are three kinds of commonly used gas nitriding processes: isothermal, polystage and resist corrosion.

Isothermal nitrogen infiltration: low temperature (480~520℃) for long time insulation, suitable for high-precision parts, but the cycle is long (about 80 hours).

Multistage nitrogen infiltration: segmented temperature control, shorten the period to 50 hours, deep infiltration layer but slightly larger deformation.

Anti resistance: high temperature (550~700℃) for a short time to form a chemical stability layer and enhance corrosion resistance.

Normal gas nitrous artifacts, the surface is silver gray, but sometimes will also appear blue or yellow due to oxidation, but generally does not affect the use.

plasma nitriding

Ion nitriding, also known as glow nitriding, is the use of glow discharge to ionize nitrogen-containing gas to bombardment the surface of the workpiece so that nitrogen atoms penetrate into the surface of the workpiece.

Specific operation procedures:

The metal workpiece is put as a cathode into a negative pressure container with a nitrogen-containing medium. After energization, the nitrogen and hydrogen atoms in the medium are ionized, and a plasma region is formed between the Yin and Yang poles.

Under the strong electric field of the plasma region, the positive ions of nitrogen and hydrogen are bombarded to the workpiece surface at high speed. Due to the bombardment of ions, the surface of the workpiece is spattered, which is purified. At the same time, due to adsorption and diffusion, nitrogen seeps into the surface of the workpiece.

Advantages of ionic nitriding:

① Can shorten the nitriding cycle;

② Nitrogen layer brittleness;

③ Can save energy, nitrogen and hydrogen consumption;

④ Local nitriding infiltration can be realized;

⑤ Nitrogen layer thickness and tissue can be controlled;

⑥ Ion bombardment has the purification surface effect, can remove the workpiece surface passivation film, can make stainless steel, heat resistant steel workpiece directly nitrogen.

nitrocarburizing

Nitrogen-carbon co-infiltration, also known as soft nitride, that is, below the iron-nitrogen co-evolution transition temperature, the surface of the workpiece is mainly seep into nitrogen.

The microfine carbide formed after carbon infiltration can promote the diffusion of nitrogen and accelerate the formation of high nitrogen compounds. These high-nitrogen compounds can in turn increase carbon solubility. Nitrogen and carbon co-infiltration can not only improve the fatigue life, wear resistance, corrosion resistance and bite resistance of the workpiece, but also simple to use equipment, less investment, easy to operate, short time and small distortion, and sometimes can give the workpiece a beautiful appearance.

Carbon seepage VS nitrous oxide

Carburization & nitriding applications