Ion nitriding is a vacuum case hardening process developed for engineered steel and cast iron parts. The hardening takes place in the plasma of a current intensive glow discharge. A glow discharge reaction or plasma reaction is set up by introducing a specific nitrogen/hydrogen gas mixture into a vacuum chamber, in which the work pieces form a cathode with respect to the walls of the vacuum vessel. The hydrogen and nitrogen ions bombard the cathode surface providing a depassivated effect, removing oxides and other contaminants. After super cleaning takes place the parts are elevated to an operating temperature 450-550^oC and a negative potential between 400 and 1000V. Parts are held for a period of time allowing the nitrogen to react with the alloy constituents of the steel. The thermo-chemical reaction between the alloy elements and nitrogen causes the hardening to take place. The parameters which determine the case depth, and type of metallurgical structure obtained are material chemistry, gas composition, time, and temperature.

Ion nitriding has many advantages over salt and gas nitriding:

1. Lower process temperatures.
2. Single-phase compound zone for greater ductility.
3. Better case uniformity.
4. Shorter cycle times.
5. The process does not pollute the environment.